I had the same issue also, I couldnt save a new plex library on a fresh plex container. I also noticed that the language dropdown on the Add Library page was empty. All I did was go to general settings unchecked any checkbox and recheck it, and click Save. I retired to add a library and the language dropdown was populated, and the save worked.
Same issue but cannot solve it
I have a same problem: Your changes could not be saved.
I canât add folders and I canât delete folders too. I accepted your advice. I did this steps, It is not worked. I tried uninstall and after than install the Plex. But this is still donât work. :@ Iâm going crazy!!! Help me PLS!
I am also having this problem now 
This also has started with my server however it will add the new tv shows just not the new movies I add to the folders. unable to delete movie folders from plex or update folder locations as i could in the past.
same issue for me as well, WD EX2 Ultra user here, with plex on desktopâŠ
I have a same problem, i cant add anything. It used to work, but now when i bought the membership, i cant add any folders 
I cant use the Plex if i cant add anything, but i still have to pay it?
This is with my Synology where the server and all files are.
I just ran into this same problem installing another server using 1.18.4. âMoviesâ wouldnât work, but âOther Videosâ did. Can someone tell what the difference is? I mean, they are all moviesâŠ
ButâŠnow in my tree it shows up as Other Videos. I donât like it.
Interesting⊠I deleted the Other Videos library and tried Movies again and it worked⊠Give it a shot.
I know itâs an old topic, but Iâm having this issue as well, right after an update to 1.18.4. Permissions are the same, just canât save any custom info now.
Same here. Been reading the forums for a bit but still no luck with the suggested fixes. Running on a QNAP NAS. My server actually went down for a week even after multiple restarts of my NAS and Plex process when I tried changing my movies directory. Itâs only just come back up nowâŠ
Things to try:
Use the hosted web app app.plex.tv instead of the local one. Donât use PMP, or Plex for Windows/Mac.
Immediately before editing the library, reload the web app in the browser (F5)
Donât change anything on other tabs when editing the library. Make only changes on the âAdd Foldersâ tab.
Thank you so much, this worked form me!!!
I had tried all other solutions but none was right.
I used chrome and went on app.plex.tv and it all went smoothâŠ
youâre mythic!!
I had the same problem this afternoon - I was just trying to change the display options for collections on a library and kept getting the âYour changes could not be savedâ message. Nothing I found here worked. I gave up and went on to other things, then got a notice that my Java needed updating. Once I updated Java, I tried again and was able to make changes to my libraries :). Posting just in case this helps someone else.
where did you update Java? On the plex server computer or on the plex player?
Iâm pretty sure it had nothing to do with Java.
Immediately before editing the library, reload the web app in the browser (F5).
For me, everything worked after I updated Java on my computer (not within Plex specifically). Maybe that was a coincidence.
Iâve recently started seeing similar problems here with PMS on my Synology DiskStation.
I had previously created an âOther Videosâ library, created a dedicated folder and pointed the library at it, and tossed some files in it to convert. This worked fine for a dozen or so videos until two days ago.
Yesterday I added more videos but they wouldnât come up in a media scan. I stopped and restarted Plex, I rebooted the Synology⊠no go. Renamed the files to something generic - still nothing.
I tried to delete the library, but it wonât go away. I created a new library pointing at the same folder, but it just tells me the library is empty (it doesnât even see the two existing files that are still showing in the first library). I successfully deleted the second library but still canât delete the first.
Iâve tried the fixes suggested here so far (untick, save, retick) with no success. I do have language dropdowns for all types of libraries except Other Videos.
IT is not resolved yet .I was a happy plex user but
Iâm having the same trouble here. Iâm a plex lifetime member and it looks like this thread has been left unresolved for quite sometime. Can someone please review this and support the solution.