u/joker200021

It seems to be fixed. I was just able to synchronize all the unsynchronized sessions by clicking on them individually in the Chrome extension. I hope it's working again for everyone now. Happy working, everyone!

I just received a reply from Seekrtech / the Forest Team that they are aware of the problem and are already working on a solution.

According to them you can get updates on their progress via Menu -> Settings -> FAQ&Support.