The fans have a tachometer to feedback the fans RPM. So either the fan is bad or the controlling logic is not working within the logic board.
I would first double check the fan cable is not damaged and the ZIF connection is properly set. I fear you may have damaged the logic board which will need access to the schematics and board view drawings as well as the skills to diagnose at the board level.
Maybe we can aim you to someone with the skills. Where do you live? Country and nearest large city.