I have this same issue; Status code 400 error for any download on iOS (iPhone or iPad) The old sync featured worked fine, have never been able to use downloads.
This is extremely frustrating. I use this feature quite often and now I’m getting the exact same error that you are. I tried to research to find out why I’m getting this error but I’m not getting a response from anybody. It seems like the plex developers do an update, they break something.
Same issue on iOS app 8.17. Both my iPhone and iPad cannot download anymore, error 409
Server is up to date
My old Android phone (app version 9.19.1.525(336a502)) can download fine.
It could be that the app on iOS has a bug
Thanks
At what point is this going to be fixed? As a Plex Pass customer I would expect that someone would care about such a major issue. Hello Plex are you listening or do you not care because you already have the money?
Update: I was looking around my iPad settings, and I saw the Plex app using 17GB+. That seemed odd given I didn’t have any downloads. I deleted my app and reloaded it. Now, downloads are working on my iPad.