Business WLAN | Problem with NTP on NWA1123-AC?

Hi

I cannot get NTP to work on the NWA1123-AC.
I have checked that the firewall does not block the traffic.

I need to activate time sync with NTP since my NWA1123-AC quite quickly get a time skew of several minutes / hours after only a month.

I have tried different NTP-servers both domain name and pure ip.
So far I have not found any errors regarding NTP in the log files.

Any suggestions?

---