ZTE Axon 7 (ZTEA2017U) won't turn on

[WheelmanM80]

The device will not boot up. Every 15 seconds, the device vibrates once and the notification light flashes once. Only holding all three buttons stops the vibrate/flash cycle. Holding any other combination of buttons does nothing. Nothing shows up on the screen during the vibrate/flash cycle. My computer also does not recognize the device when I plug it in, whether in its vibrate/flash cycle or after I hold all three buttons. I'm not sure if it's charging, because after pressing all three buttons to stop the vibrate/flash cycle, the notification light doesn't stay illuminated red or green while plugged in. Is there anything that I could check internally if I took the phone apart? Maybe a connection worked itself loose? I would very much appreciate anyone's troubleshooting ideas on this, and thanks for your time.

 

[WheelmanM80]

I understand that many things could cause this, but I'd really appreciate some troubleshooting ideas here. I'll be taking the phone apart this weekend to inspect all the connections. I have experience building desktop computers and laptops, but other than that, I won't be able to spot, for example, a gpu or processor that isn't set correctly. Any tips for what else to look for would be extremely helpful.

 

[B. Diddy]

The first thing to come to mind would be a failed battery. You could try checking the voltage of the battery, or just replacing the battery.

 

[WheelmanM80]

I took the phone apart today and I discovered that the screen's connection to the motherboard was disconnected. I reconnected it and it powered on like nothing ever happened!
Disassembly video, in case anyone else is having the same issue: https://www.youtube.com/watch?v=wqivSM0NFsc

 

[B. Diddy]

Wow, good work! Glad you didn't have to do anything more drastic.