Can't change trial version into licensed version


I bought a SmartFTP license in March last year. I downloaded a new SmartFTP version a while ago, before it worked correct. But now I can not get the program to change from trial version (0 days left) to the licensed version. I tried it by getting a new licensekey, in ApplicationData/Client2.0 I can see the SmartFTP.key file. When I try to fill in the key (Enter key), import from file, it says "Failed to load license key from file".

I also deleted the software and installed a complete new version. But I still have the same problem. Please help me out here!!!