Hi,
I´ve seen this thread which is exactly the same that happens to me now but, It´s closed so I had to open this.
I´ve written also this post but I prefer to write it here which is more specifically.
This is my setup:
Server Version#: 1.20.2.3343 (it happens also in my previous version)
Player Version#: Plex Media Player 2.58.0.1076-38e019da (Windows 10) but, also happens in other clients like Plex for Android TV or Plex for Android.
I´ve tried to restart PMS, update to latest version (above) and also restart the NAS itself.
Check the system time on your NAS. Mine was using the system time which became a few minutes out from the media player. Set both to use a NTP server so time is the same on both ends.
It suddenly started to work again… without to do anything else!
I´ve already configured a time server in my NAS but, maybe (as you wrote) was not syncronized well having the time phased out to raise this problem?
Not sure because, to be honest I don´t know which file open (between all logs files collected in the .zip attached) to take a look about that. I had some time ago also problems related with the time. Look here.
At least in the log of the NAS it doesn´t says anything about time… but who knows?
I´ll keep eyes open if happens the same the next time.