Why cannot I connect to the remote desktop?

Why cannot I connect to the remote desktop? It is a server built on windows 2008. The server is on a university campus, but on campus it can be connected to the remote desktop of the server, but it cannot be connected when it is out of the campus. why?

Reply to discussion (solution)

Does the firewall enable related interfaces? (I think it's a bit suspended)
The security method is through vpn

Whether you are connecting to a wan ip address or a lan ip address. if the lan ip address is out of the campus, it cannot be connected.

Intranet IP addresses, for example, 19X. X.

Try to reset the network adapter?

Internet cafes are on campus, and the Internet cannot even be used out of campus ~~ Check the firewall again ~~
It is recommended to use teamviewer, which is simple and convenient.

It is estimated that you are accessing an intranet server and ask what the internet IP address of the server is. If there is no internet IP address, check whether there are other servers in the campus network. map the ports on other servers to port 3389 of the server, and then the internet IP address of the server is enough.

Does the firewall enable related interfaces? (I think it's a bit suspended)
The security method is through vpn
Port 80 was blocked.
In addition, can I solve this problem by using vpn?

In addition, can I solve this problem by using vpn?
Of course! Moreover, it is much safer.
However, you must enable the vpn service.