Thank you.
Followed your advices.
After clearing everything, the app promted me with the Welcome-screen. Went right away to fetch from Dropbox, no problems.
Then I put in my Premium-email, I noticed a cloud-sync error 209997, also in Vaults view.
First thing I tried was quiting Enpass (ctrl Q), and started it up again.
Now with now issues. Thank you.
My only dilemma now is the changes to this exact vault i did before backup and clearing things. And this vault didn't have sync access for the last 3 months.
Because now I'm only runninging latest cloud version of the Vault. Can I merge with the backup I made?