Second computer won't show all connected computers

UncleAaron

I have two computers connected to my account--my laptop and my mother's. My laptop shows up on the "online" list, but when my mother's laptop is on, it's still under the "offline" list. I went through Windows Firewall and it is checked "allowed".

Both computer's are up-to-date with TeamViewer 15.1.3937. I've installed both with the "free/Non-Commercial" option.

What should I look for next?

P.S. I've had her computer connected before, with no problems. And both computers have the current version of Windows 10.