When I startup GrabCAD Print the application loads, shows the login popup for 2 secs then goes directly to the "Unable to connect to GradCAD" popup. The application will not give me time to enter my login info. Reinstalling does not help. I can login to Workbench with no issues.
I am having the same problem, it seems to be due to the fact that our Firewall is set to "strict" and is blocking it.
This page shows what you can do with and without being connected to GrabCAD's server:
I'm guessing the only way to fix this is to get your IT dept. to allow Grabcad's servers to send and receive on the network.