Connection failed -- could ot connect to server

Hi there,
I am trying to set up my bosses Samsung Galaxy tablet so that he can access his desktop. I purchased the pro PocketCloud app for android. I have entered the correct information for our server, but it will not connect. I can connect using my iPad with the exact same information, so I know it is correct.

Can someone give me some tips on how to make this work? I have read everything I can on here, and nothing is helping. WE are trying to connect via RDP.

Thanks