1. Did you read the information on upgrading before you downloaded? FlashFXP v3.0 requires a new registration key. You can request your upgrade via
https://oss.azurewebsites.net/keyupgrade.php, or you can login to the customer portal, and request from there.
https://oss.azurewebsites.net/customerportal.php.
2. What version are you upgrading from? The queue file format has changed to allow for more options. Some very old queues may not upgrade properly.
3. Again, what version are you upgrading from? Since I know you did a backup of your old data
, delete that sites.dat, and try to import from the old one, choosing the correct version of Sites.dat file.