The following diagnostic is generating:

Warning - this return will be rejected by Pennsylvania. The taxpayer signature date on Form PA-8879-P, Pennsylvania e-file Signature Authorization, is missing or invalid. The signature date is mandatory in ${screen:3.2}

Solution:

Click on the diagnostic in the Diagnostics tab or go to Details screen 3.2, in the Paperless Filing Signature, enter the 'Taxpayer signature date' or check the box 'Computer date as PIN signature date [O].'