No, I don't use the mobile App. I log in directly via my PC. But that should not be important. I can state a NTP-server, I have tried now 5 or so, but the initial time doesn't change. I have tried D-Link NTP-Server, a german and 3 austrian NTP-Server, which are very near to my place.
I use it as a WLAN-Router. So maybe he can't synchronize?