Chosen Solution
You could as well try a new cable and do like Duane suggested: connect it to the board before replacing it, and try to see if it works properly. Then replace it. You probably have a damaged or defective power/mute/volume cable because Volume Up/Down functions on the board have a different circuit from the Power On/Off circuit - UNLESS you have a damaged connector where those 2 functions meet; that would be the connector that connects the cable to the logic board; Or that connector is dirty (clean it with a cotton swab dipped in 90%+ isopropyl alcohol); Or the cable is not seated properly: disconnect then reseat the cable.
It is possible that the replacement cable is faulty or the connector on the logic board is damaged. I would try another Power cable and go from there.
These are VERY fragile. I would suggest when you buy another, simply plug it in first and check it works before doing anything else, that way you know if it is working before taking everything apart (I’m assuming you swapped it all over) Let us know how it goes :)
Is your home button working okay? If not–look for pry damage along the edge of the board under the interconnect cables next to the battery. If home button is working okay, then this is probably just a bad flex, or damage during installation, or damage to the power flex connector itself—like these smart folks above me have suggested :) jessa
