Unable to import AllData file after upgrading Windows

Upgraded OS from Win 7 to Win10. When trying to import my collection embedded in the AllData file, I get the error message "Version not supported". I've tried downgrading Basecamp with the same result. I've tried "cheating" the system by replacing the file in the Appdata/Roaming/Garmin/Basecamp/Database folder, but it is ignored. What to do?