Most commonly when this error code pops up....it is due to the inlet air pressure being too low....or having something (such as a filter or fitting) right at the inlet that is restricting flow. This could show up more often if you were piercing while the torch is still in postflow (the cooling airflow that occurs after each cut). While in postflow the torch is designed to be able to refire...but the post flow would tend to reduce inlet pressure slightly.
If you have a way of increasing the inlet pressure....do that first. Following the instructions in your Hypertherm operators manual....activate the test air flow mode....then increase your inlet air pressure to about 100 to 120 psi (while flowing).
If you are running off full line pressure.....but have your motorguard filter...or other air filters/valves, etc.....just upstream of the plasma....you should remove these items as a test to determine if they are restruicting the flow, and causing a momentary low flow condition.
Let me know what you find.
Best regards, Jim Colt Hypertherm