entering license key problem

I have recently purchased license key to use SmartFTP but cannot enter the key by any of the methods recommended. I have saved the key, but then when I click on 'enter key', I get an error message "The system cannot find the specified path"

Just tried automatic method, but get an "Error opening file for writing" message

no good . Paid for key, but cant use the program !

help !!!!!!!!!!!

Please contact the technical support by email for assistance.