need more info then that.
1. Was your account approved?\
2. Have you login in at least once to https://cloud.disroot.org
3. Do you use two factor authentication
4. What URL do you use when setting up davdroid (DAVx5 these days)
5. DO you use username or firstname.lastname@example.org (email@example.com is not correct)
Sending a screenshot of your settings would help too.