It may be your windshield. While rain-sensing wipers can be a great feature in a car, they can cause problems reading an RFID (Radio Frequency ID) sticker. When the car manufacturers metallicize your windshield to get these wipers to function, they can prevent scanners from reading RFIDs you place on the glass.
One quick fix is to have the car wash attendants get a new sticker and assign it to your account. Before sticking it down, move your sticker to a section of the windshield that hasn’t been metallicized, such as behind the rearview mirror. Tape it temporarily to that spot and go through the car wash. If the gate lifts, then attach it with the backing there.
If your windshield has never been metallicized, your sticker may just be malfunctioning. If so, simply check with your local site, and they can replace your sticker.