I installed TestFlight on my iPad so that I could install the beta app for Plex 7.1 (See https://testflight.apple.com/join/MY6JTzix). The bug has NOT been fixed in the 7.1 (20782)-version, so I used the feedback option in the TestFlight app to send a screenshot and a descripton of problem to the developers. I also included a link to this topic.
It seems that the devs do not respond; not even acknowledging the issue exists. Theyāve got our money so why should they? Maybe some 1 star reviews in the App Store about this will finally do something about it.
Totally agree MTShipp. Iāve used Plex for years and reported a good few bugs and none of them ever get fixed. All their updates only ever make Plex worse.
Ahh. Good thinking. I did a one star review on the app and in the review I linked to the post. I might do the same with TestFlight. Another thing I was thinking of doing some time today was also do a reddit post on the Plex sub. I believe iv seen Plex employees post there at times.
If I remember correctly from the days of when plex did the big rewrite of the iOS app (close to a year of no updates) it came out the plex like to keep the devs separate from the support crew so the devs donāt get abused.
Either way they need some sort of transparency on what bugs they are working on. Just a simple tag of on the posts maybe or a separate webpage listing it all out with links to the original thread. Anyway iv gotten off topic.
I have this same issue on my iOS devices. I moved to the TestFlight build of Plex on iPad but itās no different.
This feature is invaluable if you find yourself offline and donāt want to navigate all the menus to guess at what you have locally. I donāt understand why this broke out of nowhere - I have purged the app entirely, redownloaded, re-synced, and still nothing. I did file this as a bug in TestFlight.
Iāve given up on the Plex developers fixing anything. Plex isnāt worth the money anymore. Iāve switched to Infuse. Runs far better than Plex and doesnāt need to transcode any of my files.
Glad you guys reported this, Iāve spent a few hours to try and fix this. I have the same error, on IOS 13.5 (app version 7.1) . I have an iPad with IOS-version 12.4.6 and Plex 7.0) and some Android devices(app version 8.1.2.18135) and it works fine on these devices. So itās a bug of version 7.1. I do hope they fix it soon. It makes selecting a specific album of a specific artist a lot easierā¦
I assume this issue is also the reason why I canāt see downloaded playlists anymore. That stopped working basically the same time I started to see this screen.
Iāve had the same problem for about the last 2 weeks. I was hoping recent updates from either the server or my device would have fixed it, but they didnāt. I have my main account set up as the Admin and I have 2 Managed Users for my children and I have another general home user with a different email that I sometimes use. The problem happens on my childrenās device too. Here is MY current setup on MY iPad:
Windows 10
Plex Server 1.19.4.2902 (but it also didnāt work with 1.19.3.2852 and not sure which earlier ver)
iPad iOS: 13.3
Plex OS ver: 7.1 (but it also didnāt work with 7.0 or 6.12.1 and not sure which earlier ver)
User: Admin (my account)
In my Downloads & Sync screen, when I click on the Library tab in each of my libraries, I get the same screen that the OP displayed and I get it for Family Movies, Adult Movies, Family TV Shows, Adult TV Shows and Music. I can see the material only via the Recommended Tab. Also, I can access my downloaded music but my playlist is not displayed anymore.
User: Managed User #1 (my childās account)
When I click on his account and go to Downloads & Sync, I would think that nothing should appear since I have downloaded items under my own account, but the following do appear: Family TV Shows : these shows only appear in the Recommended tab, not the Library tab
Adult TV Shows: these shows appear in the Recommended tab and the Library tab
Music: music only appears in the Recommended tab
Family Movies: these movies only appear in the Recommended tab, not the Library tab
Adult Movies: these movies appear in the Recommended tab and the Library tab
NOTE: Itās strange that if my son uses my device and logs into his managed user account, that not only can he access all of my downloaded content (which I didnāt think that he should be able to see), but that the only items that appear correctly in his Library tabs come from libraries that he doesnāt have access to (i.e. Adult TV Shows and Adult Movies). I have those Adult items in a different directory and different library. Keep in mind that this used to work until a few weeks ago.
User: Managed User #2 (my other childās account)
For the previously above mentioned 5 libraries, his shows everything in the Recommended tab and the Library tab. NOTE: Again, these are downloaded and synced under my Account, so why are they appearing in his downloaded screen and why again is everything showing up in his Library tab, when they donāt even show up under mine?
User: Shared General User (has access to same directories as managed users)
The results for this user is the same as the Managed User #2
In summary, maybe I got the On this Device is Unavailable because I have Managed Users and/or another General Home User. Maybe something has screwed up when the Watch Together feature was implemented because it did seem to happen around the same time. The Downloads and Sync was working up until recently. Also, I donāt think that all users on my device should be able to see all of my downloads and be able to watch them, especially my Managed Users. Thankfully, they have their own devices.
Developers, can you please look into this and fix it?
By the way, my 2 sons also have this error (the picture that the OP posted) and they have iPod IOS: 12.4.5 with Plex OS ver: 7.0.
+1 iOS with v7. This feature should be resilient or at least tested (does Plex QA even exist?) before release. I made the mistake of trusting it and ended up on a painfully boring 14 hour plane ride with no access to synced media. Itās not the end of the world but next time I will use another app to sync offline.
Itās interesting, Iāve got the same issue on my iPad Pro, but on my phone itās working. On the iPad I have the issues with movies, but not TV shows. I too have tried deleting and re-syncāing all the content, as I did it before reading this thread. All devices are running the latest software. Iām assuming itās a database issue as the storage for the items is used, and some of the items are visible in the ārecommendedā tab. Has anyone been asked for debug logs?
The same problem here.
A few weeks ago there was also the same occurring.
After the update in the App Store it was fixed.
Now itās back. Oh no, itās back! Run for your lives! 
It is very annoying, but hey, i have good faith that it will be solved soon.
The Plex crew is very fast in this type of little bugs.
In the meantime, if you really want to see something, you can always use the search function.
Or scroll through the recommended section.
Iām also stuck with this issue. Interestingly for me is started with seeing that problem on a library actually on the server, so I removed and reinstalled the app, now Iām stuck with this on my synced Music with the āOn this device is Unavailableā.
EDIT:
After a bit of digging in the PMS logs of the app itself, this is the only interesting thing I can find:
Jun 09, 2020 10:26:21.369 [0x16e173000] ERROR - Network Service: Error in browser handle read: 57 (Socket is not connected) socket=79
Quite what that means in this context I donāt know, but this error is happening a lot and quickly, with 108 instances of that happening conscutively in a 2 second period. Other than that though, I canāt find anything else particularly problematic.
Family members getting access to content they shouldnāt have access to is a quite serious bug. Letās hope that someone from Plex soon will acknowledge these bugs, so we know that they are in the process of correcting themā¦
Iāve also got this issue, still. Started the same time as everyone else.
Plex broke this, and now itās not possible for me to listen to non-synced content on my phone, because I canāt browse the server.
Do they even monitor the forums?
Interesting twist - I got mine to fix, but it required the following steps:
Delete all synced content on the ios device (phone in my case)
Sign out
Delete app
Reinstall app
Sign in
broken library (music for me) works again. Syncs appear to work again as well.
But now I have to re-sync everything, which is obnoxious.
But at least it works?
I did this when this first occured and it fixed one of the libraries but broke another. 
Tried the new iOS TestFlight version. Still an issue. Sent a bug report with screenshot and link to this thread. Going to keep doing so till this issue is fixed.
Same here, but now my primary TV SHOW library for my server is displaying the error regardless of synced content status.
Hi,
We have discovered a bug in the app that was causing this issue.
The fix for it will be included in the v7.2 release and should be included in the latest beta build. Please let us know if itās not fixed.
Kind Regards
I just tested the TestFlight version and it seems to be fixed. Thanks