iCloud Shared Albums empty on newly bought iPad

I just bought a new iPad and was setting up everything, but in the photos application all of my shared albums are completely empty and if I add any new shared albums, they don't appear on any other device I'm logged into with the same Apple ID.

I even tried deleting one shared album on the iPad to see if that gets synchronised on my iPhone but it didn't..

What I've tried so far:

• • Logging in and out of iCloud on the iPad
  • Turning on and off shared Albums in the settings
  • Restarting the device
  • Reconnecting to the Wifi and also trying my iPhone hotspot for the iCloud synchronisation
  • Check for any updates (and updated it)

Unfortunately, none of the above worked for me and what's even worse: I wanted to see if it's and iPad related problem so I turned off the shared albums settings on the iPhone too and turned it back on again and I have the same problem on two devices now..

At this point I am making some backups on my MacBook so I at least don't lose all of the photos I have in the shared albums.

Help is much appreciated.