Hello
The PRT availability check is very simple and it only checks if there is enough material on stock.
Take a look on the following link from SAP Help for more details:
Production Resource/Tool (PRT) Availability Check - Production Resources/Tools (PRT) - SAP Library
Here, you will find the following information:
The availability check for PRTs does not check whether other orders or networks require the same PRT at the same time.
As a workaround, you can try to use your PRT as a regular component and simply avoid posting the goods movement. That way you will use the material ATP check instead of the PRT.
BR
Caetano
