Can't connect to Gateway on my laptop anymore

So, your wireless adapter is working and DOES connect to the HughsNet network just fine. Since you are not having a failing wireless network adapter it is probably a driver issue with the Dell adapter. My guess is the adapter is not working will with the newer wireless protocol the T-Mobile gateway uses. The HughesNet probably does not use 802.11ax it probably uses 802.11ac or the prior 802.11n wireless protocol version. Sorry to put tech terms out there but it can't be helped.

One way to work around such an issue is to get a newer USB wireless adapter that does support the newer wireless solutions. I had a similar issue with my older laptop and bought a USB adapter that has a newer chipset and drivers. You can argue with the OLD adapter all you want but it would probably be much simpler to just go to BestBuy or Amazon etc… and buy a Windows 10 compatible USB wireless adapter that supports 802.11ax. That is the same wireless version that the T-Mobile gateways use. You would have improved security and have driver updates due to the newer chips. The problem would be solved in a fraction of the time you spend fighting with the 7 year old adapter.

You would have nothing to lose to try it. If you buy one on Amazon and it does not work you can just sent it back. Problem solved or try another one. If you do the same thing expect the same results.