Hello,
Does your device have access to the internet?
Are you able to resolve other hostnames, such as google.com?
The issue might be related to some IPs or ports blocking on your operator's/ISP's DNS side, so I'd like you to go to Network -> Interfaces section, open your WAN interface settings, switch to Advanced settings tab and set a few custom DNS servers, such as Google's 8.8.8.8, 8.8.4.4 or Cloudflare's 1.1.1.1, 1.0.0.1.
Could you check, if your device has correct time set in the WebUI Services -> NTP -> General page? Synchronize with browser, if necessary, then press Connect again in Services -> Cloud solutions -> RMS.
You could also enable Operator station synchronization in Services -> NTP -> NTP, for additional redundancy in the future.
Best regards,