The Sutro hub cannot connect to 5 GHz. Make sure that the WiFi that you're trying to connect to is 2.4 GHz.
After connecting to the Sutro network, sometimes your phone will stop connecting to the Sutro network because there is no connectivity, and it will auto switch to your home WiFi or cell data. Try the following, and then reset your huband connect to the Sutro network again.
Change settings in phone to not auto switch to cellular
Forget home network
Android Users: When connecting to the Sutro network, you may see a notification that says tap for options. Android will inform you that the Sutro network has limited or no connectivity. Click stay connected.