Went on new Flux section of the A13-14 autoroute and assumed my Ulys badge would pick it up and pay. But no. I received a letter with potential hefty fine. Was relieved that if I paid by Friday it was regular toll cost.
I called to ask why my Ulys badge not read. I discovered that it should be ON that portion of black dotted glass behind the rear view mirror. I had positioned mine just below which worked fine for regular telepeage booths.
So be warned
Never have any problems with the bip & go.
Good to know. Our badge says it should be on the dotty zone for all use, and I think it is.
Wish we had bought one earlier it can be linked to a UK or French bank account so no problem for anyone not living permanently in France Bip&Go only charge in the months in which it is used, so not a monthly charge
Ulys do the same. No charge if not used in that month.
My mistake was thinking the black grid on windscreen would block the signal, whereas it has been created to allow a signal, because the rest of the screen has a solar reflection coating.
Yes it’s confusing, but the black dotty area is the right place!
When I got my msot recent Bip&Go gadget the instructions did say quite explicitly to put it in that section of the windscreen.
That requires reading the instructions 
Yes… RTFM
I’m not sure the Ulys had one!