Usually the cause of a license not being accepted is that it has already been registered on as many PCs as it allows. (Sometimes this will be because an existing PC has been upgraded, which can make it appear to be a different PC)
If enough of the existing PCs are unregistered (or out of date registrations for upgraded PCs removed), then the license can be used again.
You can manage where your license is registered by doing the following:
- Login to your account at https://secure.blueberryonlinestore.com/Login.aspx
- Go to the Your Licenses – Purchases and Trials page
- Click the Manage Licence Usage option next to the license your want to manage
- Use the Remove option to unregister unwanted PCs.
If you have not used all of the available registrations for your license, it could also be because you do not have the correct version installed or that Flashback is unable to contact the license server to verify your license key.