!!
critical HP

Error Code Power LED blinks red, 7 blinks with a pause

System board failure detected from invalid ROM.

? What Causes This

Faulty motherboard or incorrect BIOS/ROM checksum.

How to Fix It

Flash latest BIOS and reverify checksums. If persists, replace the system board and restart diagnostics.

Source: page 2 of the official manual

From the manual

Manual page 2 — HP error Power LED blinks red, 7 blinks with a pause

This error code appears in:

HP Prodesk 600 G1 Small Form Factor PC