Dell Precision M6700 won't turn on after webcam replacement

Hello,

I was wondering if anyone could help me with a no boot issue on my Dell Precision M6700?

I recently replaced a dead webcam on my Precision M6700, which involved a lot of digging in the machine to get to the connector. Since reassembling the machine, I'm struggling to get it to boot. I found a recommendation on the internet for laptops that won't boot:

Remove the CMOS battery.
Unplug the power cord.
Press and hold the power button for 10 seconds to fully drain all residual power.
Put the CMOS battery back in, make sure you put it in correctly.
Plug in the power cord.
Power up.

I tried this, and the machine immediately turns on for two seconds, then off. If I then press the power button, it boots like normal and the new webcam works. However, when I shut down the laptop, it will no longer boot and I have to repeat the instructions above.

I have ordered a new CMOS/BIOS battery on the internet, because I wondered if this was the issue. Any help would be gratefully received!

Thank you

James