PA is a semi piggyback state, meaning you can file it alone but it wont be processed until a federal return is filed as well...so it makes sense for PS to bounce them both back when the fed is rejected.

https://accountants.intuit.com/support/en-us/help-article/electronic-filing/state-e-file-methods-sta...

PiggyBack/State-only return:

The state return can be processed independently of the federal return. It's a common misconception that these returns aren't sent to the IRS—they are. However, the IRS sets aside these returns for processing by the states, in most cases, prior to acceptance of the federal return or the federal return being e-filed.