Sorry to hear! Have you tried clearing the unit in case air is trapped inside? Here is a guide from Karcher’s website.
To bleed the pump of any air, turn the machine off and disconnect the high pressure hose and trigger gun from your power washer. With only the garden hose connected to the machine, turn on your water source and allow water to run through the pump of the machine for 20 or 30 seconds. Turn off the water and connect the high pressure hose and trigger gun and try using the machine again.
Have a look through the above link as well.
I hope this helps in some way.