Not adding new movies/series to plex with new versions

Dear Plex Community,

I am using Plex for a few years and I always recommeded to my friends.

Since April/May last year, my Plex is not adding new movies and series anymore after I updated my Plex Server. Once a Month I tried to install a new version but everytime I encounter thesame problem.

At the moment I am stil running on release 1.15.2.793 and everything works perfect.
However, no new series and movies are added when I install a newer version.

Yesterday I tried first the latest version (1.16.5.1554) and the latest update via the synology update manager (1.16.5.1552).

Does anyone have an idea how to solve this problem ?

I am running plex on a synology ds216+

Regards Jeroen