Gearbox problem ( wont change into top)

hi i am a newbie

well i have a problem with my 96 range rover 4.6 hse.
it has been standing for about 1 year and all the computers needed resetting so i took it to my local range rover dealer and had them done. All fine except the gear box the dealer said i will need to drive it to sort it out but it wont change into top or kick down what i want to kow is, is this normal or do i have a problem? and if so how big a problem? if any one can help i would greatley appreciate it.

thanks in advance dannyp