If you are having an issue with your chemical injection working the first thing to look at is the nozzle that you are using. There are many different styles of nozzles but two of the most popular are illustrated above, the chemical or detergent nozzle has to be on the end of the wand in order for the injection system to work if any other nozzle is on the wand the machine will not pull chemical. (left side) Quick connect nozzle, plastic is always black in color and your machine may have come with 4 other quick connects that attach at the end of the wand. (right side) This nozzle is known as a vario nozzle or variable fan spray nozzle, you have to make sure that this nozzle is on the right position for the soap to work, it is as simple as turning the end of the tip until you are on the detergent setting.
If your chemical injection system still continues not to work you will have to continue with working on the chemical valve assembly that is on the pump.