TeamViewer QuickSupport app does not activate (no ID generated)

I'm working with an Android-based automotive diagnostic tool that can access the internet just fine but the Quick Support (TeamViewer QS) "USER ID" doesn't populate and a message in the lower left corner reads "Activating TeamViewer". The tool's Technical Support staff had me use a portable hot spot on my phone, then everything worked as it should have. This test proved there is nothing wrong with the tool.

TeamViewer's website support knowledge base was of no help.

Hours were spent adjusting the wi-fi router's settings and even a reset to factory settings didn't resolve anything.

So, what network setting on the shop's Wi-Fi needs to be adjusted and how??? Has anyone BTDT?

Thanks in advance!