How do I connect a Netgear Nighthawk wifi range extender to the T-Mobile internet gateway

I tried it every which way.  I split TMobile to two names.  Then I set it back to one name with the Netgear box checked.  Every time Netgear did not see the 5G network.  It saw a lot of 5G routers of my neighbors but not TMobile even with the two boxes sitting right next to each other.  I reset both devices and tried downgrading the firmware on Netgear.  After hours chatting with Netgear they told me to return it for another extender.  If I get another extender it will not be a Netgear.