Logic board replacement no fan spin

I have a 2015 MacBook air with slight water damage I first tried to replace the DC board because I was getting no light at all and the water damage indicator was red on that side. Replaced the DC board and I now have green/Amber light. Still no go I tested all voltages but decided to buy a new logic board. Received new logic board and all forums say that if you connect power and cables u should get a fan spin. I still have no fan spin. Is there something small I am missing . Just want to ask before I attempt to fully assembled and do a reset. Thanks in advance.... Only think that I have yet to replace is the fan and the ribbon cable