Unable to setup FACEID to Unlock phone

Follow the steps in this article:

If Face ID isn't working on your iPhone or iPad Pro - Apple Support

If you can’t enroll your face, take your device to an Apple Retail Store or Apple Authorized Service Provider or contact Apple Support.

Good luck!

That means you have some restrictions put on the device.

Possible screentime restrictions like from here:

Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support

• Passcode Changes: Prevent changes to your passcode

Or you have some kind of restrictions profile installed.

See if you have a profile here:

How to delete an app that has a configuration profile on your iPhone, iPad, or iPod touch - Apple Support

And lastly, restrictions might come in with exchange accounts, so if neither of the two above applies see if you have an exchange email added.

Good luck!