Never could get it to work on my 2016.5 MS. I ended up with a portable EZ pass and held it out the window (actually through the sunroof opening) and that worked like a charm.
But, on my 2022 MY, attached my SunPass (looks the same as the EZ pass) to the upper windshield just to the right of the rear view mirror, as shown in the manual. works like a charm in Georgia dan Florida. You have it in the right place if the drive can't see it.