Key Problem?

I have a 99 P38 DIESEL which when I insert the key the OBC is telling me "ENGINE DISABLED PRESS REMOTE"
I have tried many times and have only managed to get it running once. I recently bought a new refurb fob kit but although it lights when I press the lock/unlock it will not operate the door locking system!! (have also tried using the emergency key using the access code,no luck)
Now, does this mean I have a faulty key fob or does my problem lie elsewhere