License file is loaded from the run folder of your application
What are the values of:
string fileName = Limilabs.Mail.Licensing.LicenseHelper.GetLicensePath();
LicenseStatus status = Limilabs.Mail.Licensing.LicenseHelper.GetLicenseStatus();
Is MailLicense.xml file in the correct folder?
Please remember your application (the user in context of which your application runs) must have at least read access to this folder/file to be able to load
All license types come with one or two years of support an updates - are you sure that your license is still valid for the latest version?