I referred to the profile you created at Manage My Home and see you have a model number 58075206 Pressure Washer. On this model there are a couple common things that prevent the detergent from pulling into the system.
The first is the position of the detergent shut-off valve. The valve should be "on" only if you are using detergent directly from the cleaning tank. If you are using a siphoning hose, to pull detergent from another container, the valve needs to be set to the "off" position and the filter on the siphon hose should be fully submerged in your detergent mix.
The other common issue is simply the use of the wrong spray tip. The detergent will only work with the Black Spray Tip. The White, Yellow, or Red tip will not work as the pressure they produce will not allow detergent into the system. For the same reason, the engine needs to run at the correct rpm and the hoses need to be free of any leaks.
If none of that helps you may want to check your manual to be sure you assembled and purged the unit correctly. If you do not have a copy of your manual you can view it online at Manage My Home to get more troubleshooting information including a contact number for the pressure washer helpline.