It is important to note whether the laser is just weak or doesn't fire at all.
1) Test if your machine runs with the lid open without problems. If it does then there is likely nothing wrong with the control card/electronics.
2) Run a job at the upper left hand side of the work area. This position has least amount of travel and misalignment. If it cuts fine then it is an alignment issue.
3) Turn off the lights and observe the glass tube through the window. Does it turn pink at all when firing or there is absolutely no light. If there is any light, your power supply is likely fine as it has passed the plasma ignition stage. Result: Power supply is ok, tube needs replacement.
4) If you have no laser power at all when cutting, disconnect the plug from the power supply to the control board and test the tube by pressing the pushbutton switch on the power supply and observe if it fires. If you don't remove the harness to the control board, the protection switches (lid switch, water switch) will not allow the power supply to fire. If it fires then your tube and power supply are likely fine. Result: issue with the water sensor (kinked line, backwards, low water), or lid switch (wire disconnected or magnet not aligned), or laser firing mosfet is broken (rare)