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...

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...

@Mountain-Guy I have an almost identical issue. The RE220 wont' connect to TMO gateway, except my RE220 is a bit older, version 1.8 and my TMO gateway is TMO-GASE. The TPLINK Extender mobile network...