Headphones won’t turn on after swivel hinge replacement.

Wh-1000xm5’s was replacing the left hinge swivel, carried out all the steps you mentioned, but when i finished and tried to turn the power on the headphones wouldn’t turn on, checked the battery its got about 4 volts, all the ribbon cables are in the correct place’s using a multimeter meter to check before popping them into the 16 pin’s. I read online i could’ve blown a fuse somewhere not sure where. Any tips or suggestions on troubleshooting to find out whats wrong ?