Thank you, David-TP! I am not sure where to find access controls. But I was able to resolve the problem by creating another network with 2.4 GHz, following the suggestions from a T-Mobile community post, (I might have to remove the t-mobile community link to post this message?) changing-individual-channels-within-2-4-or-5-50773 I copy and paste the relevant sentences here from the post, " You want to leave this network alone and ADD a second network with the + sign at the bottom of the Network tab in the T-Mobile Internet app. For this new network, set the band to 2.4 GHz and set the WPA version to WPA/WPA2. Try connecting your devices to this second network. Use the default network for your other devices, as much as possible." It worked well! Thank you and Mountain-Guy.

here is the TMobil community link without the https part. The message isn't allowed to post with the full https. I also replaced all slashes and dots with a space community t-mobile com gateways-and-devices-37 changing-individual-channels-within-2-4-or-5-50773