Continental GT TPMS problem

[kingstanding]

Hi guys. A few weeks ago I brought all my tyre pressures up to the correct setting and pressed the TPMS reset button on the dash for the system to learn. After about 30 miles the display read TPMS fault. The car's been back to Bentley with TPMS ECU replaced, latest software downloaded all 4 wheel sensors replaced but the fault won't go away. Bentley are stumped. Any ideas?