If you windshield has an integrated sun shield ( small dark dots in the upper area of the windshield or what appears to be tinting) it will block the signal. You have two options, Mount the transponder low on the window or request a license plate transponder. The LPT is made specifically for vehicles with integrated sun screens.
2015 Freedom Express 248RBS
TV 2015 Silverado HD2500 Duramax
TST Tire Monitors
Honda 2000I + Companion
2 65W solar panels
I had a similar issue with our solera. I moved the transponder to the lowest part of the windshield. I haven't tried it yet but called ezpass and they told me the sensors in the toll booths are mounted on the ceilings. Up high so the class c overhang interferes with the signal.
We live in eastern Virginia and travel across the Chesapeake Bay Bridge Tunnel, the Chesapeake Toll Road into North Carolina and west through Richmond in our Class A towing an HHR. Never had any RV related problems. EZ Pass mounted on the windshield behind the mirror. I've always found the folks in the EZ Pass office in Gloucester VA most cooperative if a problem came up.
had this very problem we were calling in correcting ez pass bill monthly. found out there is a battery in them and they do go bad. they sent a new one and its fine. thats what i was told it could be the battery. tried every thing even held out window.