Trip computer not working

I have just purchased an Octavia 2.0TDi 54 plate and the trip computer doesn't work - ie it continuously displays the temperature and won't give the mpg etc...

As part of the pre-purchase I asked for the odometer glass to be replaced as it was slightly cracked in the bottom corner. The whole unit was replaced and as a result the computer and Immobilser had to be recoded. I was wondering if this could be the cause of the non-working or possibly a loose connection/fuse. Any other possibilites.

Hopefully it will be a quick fix that I can carry out rather than going back to the dealer.

Anyway had the car for 3 days now and if this is the only problem an excellent buy. It was bought from JCB Skoda Basildon, who have only been open a month and the service was great - I will never have to return to DF in Maidstone