I've upgraded from Win7 to Win10, then went back to Win7. All clean installs.
 
I've just tried to export a song as an mp3 and the encoder is missing.
 
Now I am expected to pay for it again in the Cakewalk store. It can't be right. I've already paid for it. How can I get the encoder back?

Run the unlock program again. There is no need to re-purchase, it is a one-time fee.

What unlock program? I can't find it anywhere.

If you haven't purchased it than you need to. It would be in your account if you did and all you would need to do is DL it and run it. 

If you have already purchased the unlock program and it is not in your store account see http://forum.cakewalk.com/FindPost/3148924
 

Thanks to all, I've found it. I was looking for it in the command center, found it on cakewalk.com under "my products".
Thanks again