Connects to remote computer and Instantly disconnects (Personal Use)

I have my computer (windows) trying to access my PI outside of my network to help a friend with his setup. He has Teamviewer host installed.

Both accounts are set up to easy access under my account name. I am able to connect to his computer, however, it instantly disconnects me.

Sometimes I am able to stay connected for 10 seconds tops.

Other times I am able to stay connected, however not able to do anything on his computer. No matter what I click it does nothing.

What am I doing wrong? What is the fix?