Can't utilize local users anymore

My plex setup is simple: Plex server (lifetime subscription) on a local Synology and Plex player on my Nvidia Shield in the same network. Since I have moved to a new Synology, I cant get other local users access to the libraries anymore. For example I allow Kids movies for the Kids local user but they dont show up there. I can see the server on the left bar but plex says no access rights (plex server has a grey globe symbol). I gave access several times. Can’t use the invite features as the local users dont have an own plex account. Admin sees all libraries.
What am I missing?

Server version?

Probably this: Plex Media Server - Security Update - #3 by PlexInfo

As a follow-up to the original report and in an abundance of caution due to a population of servers still on an affected Plex Media Server version (versions 1.41.7.x to 1.42.0.x), we have made adjustments for access to affected servers. Specifically, other users to which the server owner has granted access to the server will not be able to connect to it while the server is running an affected version. Once the server is updated to a fixed version, other users will be able to access again. Server owners will still be able to access the server as normal.

Again, we strongly recommend that everyone have their Plex Media Server updated to the most recent version as soon as possible, if you have not already done so.

The new version, 1.42.1, is now available to update through the PMS management page or you can download it here: https://www.plex.tv/media-server-downloads/