key lock barrel assembly
 

Hello, just looking for some advice.
An Audi A4 98 was showing symptoms of needing a new key coil.
I purchased a key lock barrel assembly. (schliesszylinder)
Normally I would just carefully take the coil off the new barrel and put it onto the existing barrel, with the old key etc., as that's the part that generally fails. Always works fine. However on this occasion I just replaced the the whole assembly and low and behold it doesn't work.
Would this have anything to do with the key needing programmed or something similar?
Any suggestions would be great