After years of money troubles and more than one near-collapse, the city’s flagship non-profit stage company recruited a new producing artistic director and then took 16 months off, presenting only a few imported events. Now that new boss, Paige Price, has gotten the outstanding $1 million in debt paid off and rearranged operations, and next week PTC returns to main-stage productions with Lynn Nottage’s Sweat. Will the audience return? And what comes afterward?