Invalid license key
The error message can appear if there’s a version mismatch. If for instance the version of the installed product is 6.x and the license key that you’re trying to import is for version 7.x then this can occur.
You can find out by comparing the name of the license key text file (it usually contains the first digit of the version number) with your installed version.
Open up “Apps and Features” or “Programs and features” on your server. There you will be able to see the version numbers on your installed Specops product components.
Broken or corrupt file
You can also get this error if a Firewall or mail security features have modified the license key text file content. Rows may have been moved, spaces may have been added and the encoding might have been changed.
Open up the text file and check its content. It should look similar to this, compact and with no spaces at the end of each row:
How to change the encoding: Click on “File” and “Save As…”. If it is set to “ANSI” then try and change it to “UTF-8 with BOM”, “UTF-8“ or “Unicode”. Save the file and try to import it again.