Epson Printer will not connect to 5G gateway

Have you contacted Epson support? Your model is fairly new and high end so it should work fine with your TMO router.

One thing you can try is to separate your TMO router wifi into separate 5 and 2.4G SSIDs to see if that helps. Several users have solved their printer connectivity issues this way. You can search on this community on how the separate the wifi SSIDs depending on your TMO router model, but it's generally pretty clear on the TMO home internet mobile app since it's one of a few features in setup.