Problem solved. It was the OpenTasks app.
SOLUTION: In the permissions settings of the OpenTasks app the option “Contacts” (in german “Kontakte”) has to be turned on.
Thanks for your help.
Hello. Sorry me for my very, very basic english.
I have the playstore version of your app to sync my contact and calendar with owncloud account.
When I’ve activated the two authentication on my owncloud account the app tell me that it didn’t logged. When I disable the TOTP, I haven’t got any problem. There is a method to give TOTP activated and user davdroid? Thanks you.
If you’re using two-factor authentication, you’ll have to generate a device-specific password for DAVdroid and use it instead of your account password.
Good. I try and now its ok. Thanks you. Good luck.