Hi Chrissy,
Karcher provides a set of manuals for your pressure washer here.
[link|https://www.kaercher.com/us/discontinued-machines/k-4-16031520.html|K4 Electric Pressure Washer, 1900 PSI, 1.603-152.0 - Kärcher]
Buried in the midst of those pages is one particular page that has a set of troubleshooting instructions.
[image|3396878]
Step through the Motor will not start section then come on back and let us know what you found and we'll see if we can figure out your next steps.