I noticed that HP does not provide a Windows 11 Wi-Fi driver for the Intel(R) Dual Band Wireless-AC 7260 on the HP EliteBook Revolve 810 G2 support page. Since Intel has also ended support for this adapter, this could indicate a compatibility issue between the legacy wireless adapter, the Windows 11 Insider Preview build, and the T-Mobile 5G Gateway.
At this point, I'd recommend checking whether the same behavior occurs on a stable release of Windows 11 or, if possible, testing with a compatible USB Wi-Fi adapter to determine whether the built-in Intel(R) Dual Band Wireless-AC 7260 is the source of the compatibility issue.