Some PSU has no "Test Button". So when no laser, you can not fire by using the PSU. it is very difficult to isolate the problem, not can tell if its tube, power supply, chiller or software problem.

Here is the way:
First please confirm if the psu has electric.
The method is to putting your hand near the psu to feel. Usually there is a little fan for that. And you can feel the air blow.

Second, if the psu has electric, you can have P and G short circuit.
And you can connect a wire from L and touch the pin of G.
If the laser tube is OK, there should be laser.

This method has already eliminate the factor of water circulation and safety switch. You should also check those two, they are also common reason for no laser.