Sharp Roku TV only connects to the new network

We have a cottage at Lake Erie with a Sharp Roku TV. This thing has been a constant pain. This year, for our first trip, it won't connect to any device it previously had. I have a T-Mobile 5G Hotspot that we've used for 2 years that works great here. My kids use it for the drive-up. We get here, the TV connects, and it's like having home service. 

As of last night, the TV has decided to stop working with previous connections. It won't connect to my HS or my mother-in-law's iPhone (on Spectrum/Verizon). It acts like a legit service issue, it connects, shows excellent connection, and we go to YouTube TV or any other service, it disconnects, and has the test/set up connection message. Meanwhile, these devices are working fine on the internet. The HS has 3 tabs connected and is watching YouTube videos. I disconnected them to do testing.

So this morning, I figured I'd try my S25 Ultra. Boom! It works GREAT! I switch back to the Hotspot, and wah wah wah... the connection drops, and it won't work. All I can guess is that the S25 is new, and the TV has never connected to it before today, but the iPhone and HS are usually used for connectivity.

I have like 4 Rokus (Ultra, 4, stick, and 4K stick) at home and a TV. Rarely have I had any issues, but this TV will be the death of me. 😱