License File is Invalid
When applying the license file to snappy fax, if you get the message that the license file is invalid then you can be certain that the license file you are trying to apply is not correct for the edition of snappy fax that you have installed. If you have purchased a license for the standard edition and have installed the SG3 edition then the license is invalid. Click the application button and select 'About' to see if the line 'G3 Support' or 'Super G3 Support' shows yes or no. If yes, then you have installed the SG3 edition and will need to uninstall it and then download and install the standard edition.
If you saved the license file received in your license email, the file name indicates what the license is for:
SFSG3LicenseKey.lic is for the fax server software, SG3 Edition
SFSLicenseKey.lic is for the fax server software standard Edition
SFG3LicenseKey.lic is for the desktop/client software SG3 Edition
SFLicenseKey.lic is for the desktop/client software standard Edition