Dell typically uses custom connections between motherboards and front panels, so that could be part of the problem.  If PC is working correctly despite that error message, I'd just disable SupportAssist. 
Hey all, I move all Dell internals to a new non-Dell tower case. All same components, just new case. Getting this error from SupportAssist when powering up. SA (SupportAssist) error code: 2000-0716 "Cables - check the following cable. Alert! Power button cable failure." The power cable plug on motherboard is 12 pin (with one pin missing, so actually 11 "live" pins). The new case has one power button cable but breaks out to multiple 2-pin plugs (hdd led, power button led, Power button, and Reset button), so that is 8 pins total (3 less than motherboard plug). 1) is the different pin count causing error? 2) I've found motherboard plug pin layout on the forums but wondering if I have the wrong one? 3) The PC is from late 2015, should I consider removing SupportAssist? Thanks!
XPS 8900, SA error code 2000-0716