No charge light, need help identifying which part to replace.

I have a Macbook Air 11” which suffered some water damage. Now the charge light no longer comes on. The machine still boots but turns off immediately when the power is removed. I’ve performed an SMC reset (but only heard 1 chime) but the menu still says “not charging” and battery status of “replace soon” the power supply is working as I’ve tested it with a Macbook Pro Retina .

I’ve determined it to be one of these 3 parts; IO Board, IO board Cable, Battery. I don’t have another Macbook Air to swap parts with and I don’t want to purchase parts unnecessarily.

Does anyone have some further tests to determine which part is faulty?

Thanks

Mark