Personal hotspot

Did you already contact your carrier about that? Since the hotspot option has to be provided by the carrier, you might have to update your carrier settings, as described in this article:

Update your carrier settings on your iPhone or iPad - Apple Support

Did you try to restore the phone to factory settings, using your computer, setting it up manually and testing the personal hotspot after that?

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

That’s what I’ve discovered recently with my XS.

Cellular provider claims no changes from their side.

More to add: tried to set up my old iPhone SE 1st gen. from both new phone state and from iTunes back up.

And I saw 2 different behaviors: when set up from backup: same behavior - no hotspot, but as a new phone - hotspot was back with the same sim.

It seems that Apple did screw up something with restoring settings from back up as well with some settings on live devices.

And no way to change that particular setting, resets do not help.

To Apple credit: it was first issue since iPhone 4, each new phone was restored from backup. But now it seems to fail. This anyway will occur, the only question is when. Will see how/if it will be resolved. The only viable workaround seems to have other phone used for only this purpose, nothing else worked for me.

Update after iOS 14.6: Problem remains, and my backup iPhone se has lost hotspot option gone today as well. So, it seems the option that’s remain: reset phone before usage as hotspot. Or use some other brand. I see no other option in case of need for backup Internet hotspot. Thanks Apple. :(

I've had this problem on my iPhone 7 for about a month, and I literally tried everything (I've done a factory reset 4 or 5 times).

What eventually worked for me is that I renewed my SIM card from my network carrier, I thought about doing that since I've had the same old card for the last 10 years.

and it's all good now!

hope this helps.

Did you just reset all settings on the phone in Settings/Reset? Or did you restore the phone to factory settings and tested it without the backup?