This Path was totaly missing in my Docker config, so I added it manually and now I see the logfile in the path.
This is the content:
12-20 06:04:35:699 [ info sync.accessmanager ]: 2 "" "https://owncloud.????.de/remote.php/dav/files/???????????????/Upload/ocs/v1.php/cloud/capabilities?format=json" has X-Request-ID "2f88149c-5900-4924-8bc2-720c0fb49424"
12-20 06:04:35:699 [ info sync.networkjob ]: Created OCC::JsonApiJob("https://owncloud.????.de/remote.php/dav/files/?????????????????/Upload/ocs/v1.php/cloud/capabilities?format=json", "2f99149c-3640-4915-8bc2-720d0fb49424", "2f14149c-3640-5015-8bc2-710c0fb49424") for QObject(0x0)
12-20 06:04:35:945 [ warning sync.networkjob ]: OCC::JsonApiJob("https://owncloud.????.de/remote.php/dav/files/?????????????????/Upload/ocs/v1.php/cloud/capabilities?format=json", "2f88149c-3640-4915-8bc2-710c0fb49424", "2f88149c-3640-4915-8bc2-710c0fb49424", "Error transferring https://owncloud.????.de/remote.php/dav/files/?????????????????/Upload/ocs/v1.php/cloud/capabilities?format=json - server replied: Forbidden") QNetworkReply::ContentAccessDenied "Server replied \"403 Forbidden\" to \"GET https://owncloud.????.de/remote.php/dav/files/?????????????????/Upload/ocs/v1.php/cloud/capabilities?format=json\"" 403
12-20 06:04:35:945 [ info sync.networkjob.jsonapi ]: JsonApiJob of QUrl("https://owncloud.????.de/remote.php/dav/files/?????????????????/Upload/ocs/v1.php/cloud/capabilities?format=json") FINISHED WITH STATUS "ContentAccessDenied Server replied \"403 Forbidden\" to \"GET https://owncloud.????.de/remote.php/dav/files/?????????????????/Upload/ocs/v1.php/cloud/capabilities?format=json\""
12-20 06:04:35:945 [ warning sync.networkjob.jsonapi ]: Network error: OCC::JsonApiJob("https://owncloud.????.de/remote.php/dav/files/?????????????????/Upload/ocs/v1.php/cloud/capabilities?format=json", "2f88149c-3640-4915-8bc2-710c0fb49424", "2f88149c-3640-4915-8bc2-710c0fb49424", "Error transferring https://owncloud.????.de/remote.php/dav/files/?????????????????/Upload/ocs/v1.php/cloud/capabilities?format=json - server replied: Forbidden") "Server replied \"403 Forbidden\" to \"GET https://owncloud.????.de/remote.php/dav/files/?????????????????/Upload/ocs/v1.php/cloud/capabilities?format=json\"" 403
12-20 06:04:35:945 [ debug default ] [ main(int, char**)::<lambda ]: Server capabilities QJsonObject()
12-20 06:04:35:946 [ fatal default ]: Error connecting to server