Dell inspiron 5547 won't turn on

My 5547 had damaged on Antenna cable, so I replaced cable.

I disassembled bottom part and build.

However, I can't turn my laptop on.

I followed people said that "remove battery, push power button 30seconds, and turn on" but it didn't work.

I only put cooling fan and battery on motherboard, it doesn't work when I push the power button.

What should I do?

Please help me.