CalDavSynchronizer: Error 401

I'm running cPanel & WHM v106.0.13 Since last week calDAV sincronizing stopped working with nextcloud (Error 401). As I could not identify the problem I changed synchronizing to roundcube. And now, 4 days later, I'm running into the same problem with this. Does anybody know a solution? btw: password is 100% correct, doublechecked