Have you finished completing the PA return? It will often start as taxable but during the interview, you will be asked: "What kind of retirement income do you have from Pennsylvania?" From the drop-down menu, you can select a designation which fits your pension, including a default option for "I'm eligible, Plan's eligible. No PA tax"
See attached screenshot (note you may need to click edit next to your retirement income source on a Retirement Income Summary page before you get to this screen)
