Chosen Solution

HP Chromebook 14 G4: Power On/Off light on left hand side of unit stays on for 10 seconds, then goes off for 3 seconds continually. Have disconnected battery, still does the same thing.

That model is older and the batteries by now are not as good. I would run a battery test in Crosh. https://www.howtogeek.com/309971/how-to-… If the battery health is at 85% or below replace the battery. If the new battery doesn’t fix the issue than the issue is with the board. I work for a school and we have several of these devices. Most are parts now and the ones out are stubborn to go to a smaller screen due to battery issues or they got lucky, and have a good device.