K40 laser power lost

hello is there someone that can help me please?

my laser is a k40 40w
the laser has lost his power, so i open the machine where the lasertube is.
when i touch the lasertest button, then is there only a beam in the tube and not true de mirrors

so i open de elektro kast and touch the test button and then is there the beam true the mirrors
how can i solve this?