This error is caused by a corrupted license file.
Vizit™ license file is an XML document, so any changes to the file contents (including adding/removing whitespace) can break the license file structure and make the file invalid.
Normally you can experience license file corruption after downloading it using Outlook Web client. The workaround is to not use Outlook Web client for downloading the file and copy the license over from your desktop.
Normally your license file should be about 400-1000 bytes and should look like this:
<?xml version="1.0" encoding="utf-8"?> <License> <Assembly>VIZitSP</Assembly>
<Name>Your name and email here</Name> <Expiration>expiration date
here</Expiration> License options here <Signature>Digital signature