Air Assist stopped working

It is most likely the air pump went bad, the power supply for the pump went bad, or the connector came loose. Not a software problem.

You need to set up the correct M Value in Lightburn. It is either M07 or M08. It is somewhere in the settings of Lightburn. To test it, just type in the console window M07 or M08 and check which one activates it. M09 switches it off again.