Key not opening roof

[Dug]

Hi Chaps I have only had my CLK a few weeks and had minor a problem (the head restraint would not go up and down) the dealer sent it to an independent Merc specialist who reset the electronics all came back working except the hood would not retract from the key any more? it went back in for another reason and asked them to check it out as thought there may be something in the electronics that needed to be set to operate the roof off the key,they said that there was nothing that they could see as an option, but said it did not see the infra red signal from the key?
Are they telling me twaddle ! thought if the infra red not working it would not work in the ignition? only have one key! I know I should bite the bullet and by a spare but but they are £220 !!