Some first-time Registration keys are issued with a built-in expiration date.
This is done automatically by the payment system when orders/payments show inconsistencies (not matching data with your registered credit card data). Please don't be offended, because there are many legitimate reasons for an inconsistency in your order data (simple typo's for example).
What this does allow however is us to shut down fraudulent purchases using stolen credit cards. This is one way we protect the FL Studio community from illegal customers entering the forums, long term.
Make sure you actually install/run the newly downloaded registration key (FLRegKey.Reg), so it can write its information in your PC Windows Registry. This action should bring your FL Studio into a fully registered state again. To install, double click it or right-click and select 'Merge'.
If this doesn't work, it means that your information in our database hasn't been updated automatically yet. Please notify us of this problem using our FL Studio Ticketing System.
To get to the Ticketing System, first sign in to your online 'my account' page. Then select the tab 'tickets'. At the bottom of your existing support tickets list is a button 'Add Support Ticket' to create a new private message to us.
Please mention your "Registration will expire" as reason for contacting us. We will correct the problem and you will be able to download a new registration key to get your problem solved.
We apologize for the inconvenience, and hope you understand our position.
Please note, if you have been through this process once, your registration code will not expire again for the current version of FL Studio.
The FL Studio Support Team.