How to resolve iPhone hotspot problems with MacBook Air?

Two iPhones: both use Pure talk Provider, both iPhone SE's, one shows up as using LTE, the other on 5G. I do not understand why or how to change or affect that. The 5G connected phone will no longer(always has before today) connect to hot spot; also the 5G has only 1 bar signal in this area, while the LTE has 3 to 4. Rural area, yesterday in more urban areas but was not attempting to use the hot spot-- on my WIFI router at home. My iPhone works just fine for telephony and text messages and maps and browsers.

Both myself and electrical engineer friend tried "everything" and could not get my iPhone and MacBook Air to "stay" connected. The odd thing is the control center SHOWED a connection buy really, nothing would work as to browsers, email, or Map app. Randomly, the control center eventually showed "no connection", causing me to re-do all over like ground hog day. Finally, I gave up. When a 3rd iPhone showed on the scene it connected fine. The two iPhone's that DID connect and run a hotspot were 10.4.1 and 10.3.2 iOS; mine with NO ability to connect was iOS 10.4.1

I have no clue, tried "everything" even "resetting" the General/ Network settings.

Suggestions?!

Ha! this is crazy.

[Re-Titled by Moderator]