Hello Lou! We are glad to hear that your Zevo Flying Insect Light Trap is getting rid of the gnats and we understand your concern about the refill change. Regarding your concern, please make sure the curve of the cartridge lines up with the trap's shield. Align the gray prong-like piece of plastic on the bottom of the refill pad/cartridge with the corresponding slot in the trap. This piece needs to be inserted into the device to activate the light once the refill pad/cartridge is plugged in. Your feedback is highly appreciated as it help us improve our products in order for them to fulfill your needs. If you would like to share more of this experience, please contact us at the number (866) 215-1297 and our team will be more than happy to take your insights and help you with any question or concern that you may have. Have a nice day.