For some reason your phone cannot get the server address. Probably a DNS issue. Here are some ways you might be able to fix this:
- Disconnect from your VPN if you have one and see if the VPN's DNS is not resolving the address.
- If you have private DNS set, change back to automatic temporarily (Settings > Network & internet > Private DNS) to see if that's causing the issue.
- Try using another network (try 4/5G connection, a different wifi connection)
- reset network settings following these instructions: Settings > System > Advanced > Reset options > Reset Wi-Fi, mobile & Bluetooth.