"Error while validating license. Details: The type initializer for 'Act4Outlook.Lic.QLicenseManager' threw an exception" when opening Outlook

You may receive the following error when opening Outlook:


Some of the known causes of this error are shown below.


Low Disk Space

If the C:\ drive of the PC, or the user profile disk (if running RDS Server) is low on disk space, this error can be thrown at startup. To fix this, please clean up old unneeded files, and try opening Outlook again.