There are 2 slightly different ways to use Paratext modules when printing with PTXprint. One is to select the appropriate XXA ... XXG book, and hit print (this method relies on Paratext to gather the pieces together for the module, and passing the "expanded" module to PTXprint to produce the PDF). The other method is to directly name the module file in PTXprint (the 3rd option "Bible Module" on the Basic tab), so that PTXprint expands the module definition for you.
Have you been able to try both options? I suspect that the 2nd might give you the result you want; but if not, try the 1st option [I'm not in a position to test each one right now].
Something else to check is whether or not the following command has been included in the module definition:
\inc s
For more details, refer to the Paratext Help topic: "What is the specification for a Bible module?"