How do i stop wait secure on my Nissan primera?

I recently took my stereo out, and was going to replace it, with an identical one from ebay, and it stopped my imobiliser from working, which cost me £85 to get the imobiliser recoded.
I then put the original radio back in, and i now get Wait, for a minute or 2, and then secure, and nothing else.
I left it on for 3 hours, hoping it would then ask for the code, which it didn't, and still showing secure.
I have a Nissan Primera 1.8 2001 model.
If anyone can help please, i would be very grateful.