This week’s problem was to make working Remote Desktop Gateway located behind a NAT. Here’s the lessons learned:
- Issue an SSL certificate with the subject matching public DNS name (FQDN)
- Use the default port 3389/TCP, otherwise SSL certificate’s name won’t match FQDN returning an error:
The computer can’t verify the identity of the RD Gateway.
or if you put it to current user’s Trusted Root Certification Authorities:
Your computer can’t connect to the computer because the Remote Desktop Gateway server address requested and the certificate name do not match.
- Publish on the firewall, i.e. make available from outside, HTTPS port 443/TCP. Otherwise connection won’t be established returning another meaningless error:
Your computer can’t connect to the remote computer because the RDG server is temporarily unavailable.
That’s all, folks!
Alexander Batishchev's Blog 
I am facing the same issue, Can you please explain in detail or share detailed procedure to resolve this issue
What’s the error you’re getting? Have you tried the instruction I provided?
Actually I’m not an expert I’m this area. The blog post is 7 years old. I got it working and blogged how I got it working, that’s about it. I even don’t remember all the details now. So I unlikely will be s good help on this issue, sorry.
My scenario is client machine using nat ip to call Remote Desktop Gateway Server and the firewall convert nat ip to actual ip.so I generated SSL for internal ip and installed in client computer then the error is as shown below
Your computer can’t connect to the computer because the Remote Desktop Gateway server address requested and the certificate name do not match.
When I generated SSL for nat ip and installed in client computer the error is as shown below.
Your computer can’t connect to the remote computer because the RDG server is temporarily unavailable.
I think the latter certificate is the right one. The error you’re getting indicates that it’s a firewall issue now. Try to allow everything first to make it working, then start to disallow to see when it stops working.