I tested the license key listed in your account and it works without any issues.
Please make sure you're using an authentic version of FlashFXP downloaded from our website
https://oss.azurewebsites.net/download.php and verify that the key you're entering matches the one stored in your account profile
https://oss.azurewebsites.net/portal
If you're still having problem please contact us using the
contact form and include your license key.