New or used? If used it may have originated in one of the locked out countries (it can be common for people to buy iPads from those countries, not realize facetime is disabled and cannot be installed, to then sell that device and purchase one from another country that has the program)
If used that may be the case, if new then it may be an idea to take it to an authorized service provider and see why it’s not on there. If Screen Time is on I believe facetime is one of the programs you can block as part of that, so if you’ve set up screen time you can look in those settings to see if it’s blocked.