Clogged from build up, as in not cleaned after every job, or clogged from foreign materials?
From build up: after turning off your machine run just water through it for 5 minutes, your pump will cool off while you do a last inspection with home owner.
Foreign materials? Whay kind of strainer/filter u use to suck the chemicals?, if you use those plastic ones with the nylon mesh, it could be it. Dont use them, use a metal one.
I use the same injector for the past 3 years.