Just a quick heads up for those seeing this.
There seem to be issues with the Windows firewall on Server 2019, especially around NPS and port 1812.
(I have not checked other ports, but the issue may also apply elsewhere, so give me a heads up if you find other similar issues)
I have seen this around now when configuring NPS for use against Citrix ADC for use with MFA.
After installing the NPS role on the server, the default 1812 port is open.
After configuring the service to use against the NPS you get trouble connecting to port 1812 for Radius.
Checking the firewall on the NPS server shows the inbound rule enabled after installation:
But, it is not enabling connections.
So, the quick fix is just to create a new inbound rule for the UDP 1812 rule:
Make new rule
Ryle Type = Port
UDP as protocol, and 1812 as port number, you can also add port 1813 in the same rule
Choose when rule applies
Give the rule a Name, click finish and your set.