info HP

Status Power LED off - Disconnection Indicator

The machine is powered off or disconnected from a power source.

? What Causes This

Unplugging, shutdown sequence initiated, or connection issues with the electrical outlet.

What This Means

Reconnect the cable or check for proper connectivity in the outlet/socket before rebooting.

Source: page 43 of the official manual

From the manual

Manual page 43 — HP error Power LED off - Disconnection Indicator

This error code appears in:

HP Samsung Xpress SL M2020 Laser Printer Series