Bosch aquatak power washer will not start

Check to make sure the outlet (power supply) is energized. This piece of equipment is supposed to be used on a ground-fault protected circuit, so make sure the ground-fault on the outlet didn't trip or the circuit breaker (fuse) at the electric panel did not trip (or blow)
Check to make sure you are going through the proper starting procedures as outlined in your user's manual on page 8.
Follow the troubleshooting tips on page 10 of the user's manual.
Beyond that, Bosch requires that you have your power washer repaired at an authorized / qualified repair center.
I did locate a web site that shows an exploded parts view of the pressure washer, if that helps. http://www.magic-parts.co.uk/acatalog/BOSCH-Aquatak-1200-Plus.php
In case you don't have a user's manual, you can view it at: http://www.manualslib.com/manual/537062/Bosch-Aquatak-110.html#manual
Best wishes on your project.