Replacement logic board does not power up

My Macbook developed serious problems with display:

white horizontal lines and screen image oscillating up and down

I was told I needed to replace the logic board. I bought one from another

provider because iFixit was out of stock.

I received the replacement and followed the step by step instructions

to remove the old one and install the new one. I am quite sure that in

going over the steps that I re attached all the connectors. But some of

the ribbon cables are more difficult to reconnect that to disconnect.

The only power connections would be the battery cable and the magSafe

card.

The machine does not power up. The ac adapter connector initially did not come

on. But after wiggling it a bit it did come on to green.

I took the battery and bottom cover off again to inspect the battery cable connection

and it seems seated. I was carfull not to twist the cables so they connected in reverse.

Does anyone have any other suggestions? Or could this logic board be defective?