!!
critical HP

Error Code Red LED 3 blinks every second followed by a 2 second pause

The processor is not installed or detected.

? What Causes This

Processor failed to initialize, possibly due to incompatible hardware or loose connection.

How to Fix It

  1. Verify and replace the processor if necessary.
  2. Ensure proper seating of CPU socket components.
  3. Contact service to confirm compatibility issues.

Source: page 4 of the official manual

From the manual

Manual page 4 — HP error Red LED 3 blinks every second followed by a 2 second pause

This error code appears in:

HP Elitedesk 800 G1 Small Form Factor PC