PLEASE HELP WITH PSP!!!?

Okay, my friend borrowed my PSP 2000 with 5.50 Gen-D CFW and a pandora battery. However, when i got it back, it wouldn't work. I took out the battery and plugged it into the charger and it turned on, but it wasn't running CFW anymore. it was on OFW 5.50. PLEASE TELL ME WHAT TO DO!!!! IT DOESN'T TURN ON WHEN THE BATTERY IS IN!!!