2018-09-07 18:40:42 3 [ui.setup.DavResourceFinder] PROPFIND/OPTIONS on user-given URL failed
EXCEPTION at.bitfire.dav4android.exception.UnauthorizedException: HTTP 401 please authenticate (incorrect login or password)
So it’s a password problem. Do you use two-factor authentication? Are you absolutely sure you have entered your username/password correctly? Are there special characters in your password? Did you try with an app password generated by Yandex?