After a few emails to ACO and also ticket office they helpfully sorted the site for me and membership is recognised.
Recognises me now - but did have to click the dark blue LOGIN or ME CONNECTEUR button to the left of ADD TO BASKET/PANIER buttons after Logging in for first few visits to fire up the ACO ticket drop downs.
The error screen is funny/made me laugh though - OOPS with screen full of marshals sweeping the track