https://www.intel.com/content/www/us/en/support/articles/000087598/intel-nuc.html

This blink code indicates “It is possible that the power circuit has failed on your Intel NUC.”

To troubleshoot this state, remove the circuit board from the case to get access to the top of the board, with the CPU, fan, power switch, etc.

Inspect for damage or contamination such as liquid through the power button. Clean power connections using electronics contact cleaner.

Try:

• Remove and reseat RAM and SSD
• Try another power adapter compatible with your device (https://www.intel.com/content/www/us/en/support/articles/000007053.html)

Missing content:

• multimeter tests
• is the power module reparable?
• is the switch reparable?
• test using external power connection on board?