Unable to activate Hot Spot when I insert my SIMs into certain iPhones

Hello,

I I have the new Elite Unlimited plan with 3 lines.  I have a Galaxy Note 10+, iPhone 8, and iPhone 7+.  The Hot Spot feature works fine with the Note 10+ and the iPhone 8.  However, it does not seem to be "enabled" for my iPhone 7+.

I then took the SIM card out of my Note 10+ and inserted it into the iPhone 7+ and I got the same error message that it was not enabled.  I then proceeded to take that SIM card and inserted it into an iPhone XS Max, and again, I got the same error message.  To test it further, I took the SIM card that was in the iPhone 7+ and put it into the iPhone XS Max, and also got the same error message.

So, for some reason, it would seem that my SIMs are not enabling the Hot Spot feature on at least 2 different iPhones even though the SIMs allow for it on my Note 10+.  More interesting is that I have no problems on my iPhone 8.  It just seems to be at least these iPhone 7+ and the XS Max.

All iPhones are not locked to any carrier.  Also, to ensure that the iPhones weren't at fault, I put in my T-Mobile SIMs into the 7+ and XS Max, and the Hot Spot worked fine.

Is it possible there is something on my account that is preventing certain iPhones from having the Hot Spot enabled?  Are the SIMs bad?  (But why would it work fine on the Note 10+?)  Some background on this - I just recently moved to this plan as I was on the very old grandfathered legacy unlimited plans from over decades ago.  Could this be part of the reason?

I come here because when I have tried to resolve this through Customer Service on Twitter, they kept sending me to the FAQ and the troubleshooting pages that do not resolve anything.  I am trying to resolve this w/o spending the time to dial 611 if possible and hoping that someone from ATT can see this and know what the problem might be.

Thanks.