Why is my front camera not working after I replaced battery?

I watched some tips on the youtube which showed how to replace the battery briefly without removing the LCD. I did exactly the process with holding the LCD 90 degree throughout the time replacing. When I assembled the phone, I figured out that my front camera just show a black screen and couldn't take any photo, It still fine when switch the rear camera to the front camera, and the rear camera was fine. One thing I noticed that when I placed the battery inside and run the camera my phone keep restarting few times. I wonder where the problem was? My front camera or when I replaced the battery there was some shorting happened and it affected to the IC on the main board which control the front and rear camera?

Anyone can help me? Thank you so much! Cause now I'm very confusing, if I order the new front camera to replace will it solve the problem? or the problem came from the main board?