Hello,
Thank you for posting in the Microsoft community forum.
May I know if you are accessing the remote server from an external network (configured with VPN or port forwarding)? Has the network environment changed recently?
If this is an occasional problem, try restarting the local client and network device to see if it can be restored. In addition, check whether the firewall blocks remote desktop communication. You can temporarily disable the Windows firewall and any antivirus program in a non-production environment for connection testing.
Reference:
Error with connection "We couldn't connect to the remote PC. Make sure - Microsoft Community
I hope this helps. If you have any follow-up questions, please contact us.
Best regards
Jacen