got new key from dealer on 2003 BMW 745Li

i just bought new key for 03 745 li , on dashboard it says wrong key i called dealer they verified with vin number key any ideas to get veh started also they told me to hold key in for 5 to 6 seconds but no luck

Asked by for the 2003 BMW 745Li
if you BMW does not "communicate" with the new key, you will need to have it diagnosed. the 745Li is an extremely complicated car, more than all other BMW's. suggest either the dealer or a well-qualified BMW specialty shop that has the factory software.