I think your issue is that this return has an overall loss at the federal and Maryland level.  Which then means no PTE tax is being generated at the state level.  If no PTE tax is calculated, there will  not be a PTE credit to pass thru to your shareholders. 

This is not a withholding tax.   The entity is being taxed at the state level.  The income then flows thru to the shareholder via the K-1.  But then the shareholder receives a credit for any taxes paid at the entity level.  

The entity would be getting a refund for any estimated taxes paid in this scenario.