Can’t connect to my own hotspot

I am using cellular data. All good. All apps have access to the Internet. Then I turn on my personal hotspot so others can use it. Indeed, they can connect and have network access. But, that causes MY phone to not have network access. WiFi is turned on (others can see and use hotspot) but my phone does not see its own hotspot.

I have Reset Network Settings and the phone is not connected to any network. If I rescan for networks, my hotspot does not show up and if I manually enter its name and password I cannot connect.

It seems that I can either use cellular data on my phone OR open the hotspot, but not both.

What am I missing?

iPhone 13 Pro, iOS 17.2.1