Thanks for your patient help!
Yandex.ru CardDAV contacts
Did you add the contacts to the “Phone contacts” group in the Yandex Web interface as described here?
Only the group “Phone contacts” in the Yandex address book will be used for CardDAV (i.e. be synchronized with DAVdroid)! You can assign contacts to other groups and “Phone contacts”.
Does that help?
I added “Phone contacts” group but nothing happened.
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) at at.bitfire.dav4android.DavResource.checkStatus(DavResource.kt:273)
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?
I entered password/username correctly, that is not a problem.
Finaly, I solved the problem. Thank you very much @rfc2822. I generated password with Yandex app password and everything working with that password. I don’t know why is problem with my standard password .