Engine help with new transponder key

[Dav1]

Hi

New on here hopefully someone can help. My girlfriend has a new shape Beetle 2000 model. It came with one 3 button key in terrible condition. I bought a new one from Ebay. Bought top half with blank blade and bottom half with matching code to make one new key. I had the blade laser cut to obviously match existing blade. I then coded the key and it will lock and unlock the central locking on the vehicle. However, when the vehicle is started the engine will start and run but will then cut out. Can anyone tell me how to code the key to start correctly without having to go to a VW dealer?
Thanks

[ini]

The transponder chip hidden in the top part of the key is most likely still 'immo2'.

An auto-locksmith will sort it for you, or if you have suitable hardware/software to extract the immo pin, you can add it yourself.