Client doesn't start

Its my first problem with Nextcloud client

My Nextcloud client 3.3.4.20210920 on Win 10 64bit doesn’t start. Not better if I use " Repair" . Not better if I desinstall and reinstall.

But when I open another session it is OK. I think that some key in Register stay active.

How can I clear all the entry of the Register without danger ?

Thanks