It could be the phone, but it could also be the carrier/service provider. Some of them do not allow using a device as a hotspot.
Try turning on the phone in "Safe Mode" and see if you can access that setting in there. If it will let you, then there is a software problem. If, however, it won't let you turn it on then either, I would check with the carrier/service provider and also the manufacturer about the issue, and, ff necessary, have them replace the phone.
To get into "Safe Mode" please do the following.
1. First turn off the phone.
2. Next press and hold "Power" until you see the manufacturers logo on the screen, then release the power button.
3. "Quickly" press "Volume Down" and hold it for few seconds until you see the message "Safe mode: ON" or something similar.
4. If you wanted disable it, simply repeat the steps above, and you should see "Safe Mode: OFF" rather than on.