Diagnosis
A sudden, complete loss of pressure almost always points to a failure in the high-pressure hose or a connection, not the pump itself. You've likely developed a leak under pressure.
How to Fix It
Do a visual inspection with the machine running. 1) Check the entire length of the high-pressure hose for any bulges, cracks, or wet spots spraying a fine mist. 2) Check where the hose connects to the pump and to the spray wand. Tighten those connections by hand—they don't need a wrench, just make sure they're snug. 3) The O-rings inside those quick-connect fittings can fail. Turn off the machine, disconnect the hose, and inspect the small black O-ring. If it's nicked, flattened, or missing, replace it.
If That Didn't Work
The issue could be internal to the spray wand. If the trigger valve inside the wand is stuck open, it won't build pressure. Try a different nozzle tip first to rule that out, then you may need to disassemble the wand to check the valve spring and seal.
Heads Up
Never try to repair a ruptured high-pressure hose with tape. The pressure is too high and it's dangerous. Replace the hose.