The new design Airwick Freshmatic is actually a bit smarter than the old one. It has a small light sensor inside the unit (near to the actuator) that looks at the nozzle on top of the container. If you have an original Airwick canister you will see black stripes on the side of the nozzle and when these move past the sensor (when the nozzle is depressed) it tells the unit that you have an original canister and "all is well". However, if it doesn't detect the strips (which it won't if you are using cheaper replacements) then it shuts down and the red light comes on.....!

In addition, Airwick have changed the size of their containers (made smaller) and reduced the size of the recess in the Freshmatic unit so it is very difficult to fit non-original containers which are larger.

There are some fixes for the problem. One is to take the spray nozzle off an original container and put it (with the stripes) on a non-original container. The other is to either stick a label on the side of the nozzle and put on stripes with a felt tip or put stripes directly on the nozzle. You will have to force the larger container inside the Freshmatic unit however........