I found the solution posted here:
eventually worked for me.
I encountered several issues when going through these instructions but finally succeeded to reset my cloud profile by pulling the internet plug from my pc while MSFS was loading which apparently made MSFS create a local profile instead of working with the cloud profile.
Key is that you get MSFS to ask for either LOCAL or CLOUD profile on the next start. Choose LOCAL and a new cloud profile will be created. Issue solved.
There should be an option in the MSFS data settings: “Reset Cloud profile”. That way such an issue could easily be handled.