This also happened to my friend. My conjecture: Meta automatically created a "digital profile" of your father based on his email address, phone number, full name, birth date, residence, and other relevant information that all combined would likely identify him. This means that Meta may have permanently banned your father's (and my friend's) overall identity from its servers, which is, of course, very troubling. So here's my advice to your father and everyone else:
My friend got around this by creating an account that doesn't use his real name, doesn't have his real birth date, and he provided no other information (i.e. residence, education, work, dating status, or even specific/preferred gender). Also, create a brand-new email address specifically to use on FB, and do not provide your phone number.
My friend also lost his Instagram account. Both were linked under one Meta account. Do NOT link your Instagram and FB accounts! If Meta disables or suspends one, your other will also go down.