I replaced 3 tpms sensors and valves on an 04 Cayenne turbo (the 4th had already been replaced). The sensors are TMP77 by intermotor and are supposed to be the correct sensor. I have reset the tire size and the system went into learn mode. After a while, it said no warnings but no tire pressures show up on screen, just dashes. Then a warning msg pops up saying I have a flat tire (on all tires). Do the new sensor serial numbers need to be entered into the computer at the dealer? I have tried changing tire size and relearning several times; all with the same result.

thanks!