Serpentine belt snapped- 02 protege5

Brand new serpentine belt snapped, my cars been squealing for some time and it happens when I first turn on the car and have my headlights on. I think it’s the belt slipping bc my water pump and alternator are brand new. Just put on a new belt and it’s already squealing again. My tensioner is automatic, anyone have an idea of what it could be?