Remote Desktop connection need help

hello everyone,

I have a problem with my remote desktop connection. I try to access my server using remote desktop but an error message says:
1. Remote connection might not be enable in the at the remote computer(server).
2. The maximum number of connection has exceeded at the remote computer (server)
3. A network error occured while establishing the connection.

I have checked the setting for the server and the remote tab is enabled, also there is no other remote users currently connected to the server as everyone else receive the same error message.
I try to ping the server but I cannot receive responses. The server that I was trying to connected is connected to a router and a firewall.

Thank you.