Requests for Pro Subscription when already a paid subscriber

The app eM Client pops up a window on start-up requesting for upgrade to Pro when I am already a paid subscriber. Please advise

Please go to Menu > Help > License and click on Activate.
Paste in your Pro license key.
If another license is already activated, like a Free license, first click on Deactivate.

I have paid for the program and changed computers And lost the activation code I need to get it back.
Can you tell me how? Thank You, Joseph Millman

They in lies the problem I don’t have my activation code. If I did there would be no problem. How do I get my activation code back?

Is it possible to send me my Activation code?

If you have lost the key, go to our website (Support > Lost Activation Key) and enter the registered email address. The key will be resent to you.

You will find that here.