Remote Desktop Connection

I recently purchased the Netgear LTE Modem 1120 so that I can use it along with my ATT cell phone as a backup for internet service should my regular Verizon FiOS go down.

When I look at the instructions for configuring it, I am able to get an internet connection - no issues there.

My only issue is that we use Remote Desktop for some of our offsite employees to connect to our server and I cannot get that functionality to work; i.e. I cannot connect to our server via Remote Desktop when using the LTE connection.

Is there something more that has to be done at the server level in order to be able to allow connections via remote desktop?.

We are running Windows Server 2012 on our server

Many thanks for your assistance.