I’m an American Expat living overseas with a permanent abode. I am self-employed for a company based in Pennsylvania. Do I owe PA state tax if I never physically worked in PA and received a 1099-NEC?

Assuming you are a non-resident of PA, that income is not taxable by PA.

PA Code Section 101.8 (e) states:

"Compensation for personal services rendered by a nonresident individual wholly without this Commonwealth is not taxable regardless of the fact that payment may be made from a point within this Commonwealth or that the employer is a resident individual, partnership or corporation."

https://www.law.cornell.edu/regulations/pennsylvania/61-Pa-Code-SS-101-8