50w laser not firing

Hi I'm new here and after searching threads I thought it best to ask. I have a 50w Chinese laser, I've had it since July and service it myself regularly. However last week I was in the middle of cutting and it stopped cutting (still moving on both axis just not cutting) I checked the tube and saw it wasn't lighting up so ordered another one-turned out to be a faulty tube so ordered another) This new tube fired once then nothing, the power supply does have power at the points of the laser, its showing up on the power screen when doing laser test, water protection is working, everything else is also working fine. Is there anyway to test the tube or could it be a faulty power supply as seen the voltage but only have a low voltage mma to test with or common stages of testing
Thank you