I have been having this same issue with several other iPhones including my new 15p.This is What happens when I turn on the hotspot my Roku Tv and my 9th generation ipad doesn’t always detect my iPhone hotspot with numerous try’s,so I reached out to T Mobile regarding this issue and they told me that my account was working fine and they didn’t see any issue,we did everything possible in troubleshooting to fix it but it keeps acting up.So my question is could this be a ongoing Apple software issue that has not yet been fixed ye.TIA