I'm writing this post because I've gone through all the usual troubleshooting tips and I'm at an dead end.
I was cleaning up my DS216j and checked if there were any new updates and stumbled by accident that the NAS didn't auto update to the newest version as per the release notes for that model. It was stuck on 7.1.1-42962 Update 6 so I manually updated it to 7.2.1-69057 Update 1 as suggested by the notes and here the issue began.
I knew something was off as soon as I saw the app images corrupted
Going to the package center it can't connect to it and is throwing the following error:
Connection failed. Please check your network and time settings, or refer to this article for further information.
For pretty much any app it throws the following description:
DSM update can't do a version check and is failing as seen below
Synology service status page says everything's up. The device itself has access to the internet (NTP syncs time, Configuration backup is working) and I can curl webs sites from synology normally via SSH so I'm a bit puzzled.
EDIT: Upon digging a bit further on the Synology forums it appears I'm not the only one affected as there are other reports for pretty much the same thing
It seems they are silently fixing stuff on their end, packages are being repaired in Package manager and version check is working normally
On the safe side better to wait out for a few days for things to stabilize but it appears everything's getting back up