If your hp laser printer displays an error 50.4 message, it is because of power supply glitches. You are required to follow the given steps hp printer support assistance:
- Disconnect your printer from the UPS.
- Disconnect your printer from the power strip.
- Connect your printer to a wall outlet
Keep in mind that the power requirement of your printer may harm the UPS.
hp printer support assistance
If these steps don’t turn out to be useful, then all the printer’s components are connected properly.