Did you try Hard Reset, I understand you unplugged the connections and plugged it back but you still failed right? Well hard reset is very similar to this and fixes common problems like these. check it out!
- Disconnect everything from your printer (unplug all the connections)
- Press and hold the power button (your printer power button) for atleast 15 seconds and then release it.
- Connect it back up and power on.
Next Download this "HP Print and Scan Doctor" (This is an Auto-BOT, which troubleshoots)
Next wait for the results and let me know, I'll be waiting.