• Unable to upgrade to Snow License Manager (SLM) 9.1 through Snow Update Service (SUS). Tried with offline package but that didn't work either.
• The error in the log is:

2019-04-24 10:42:43,749 [InstallationWorker] DEBUG SnowSoftware.Update.Data.RegistryManager [(null)] - Trying to set value UpdateRevision on key SOFTWARE\Snow Software\Snow Update Service\Installed Products\SnowLicenseManagerEnterpriseEdition to 401.
2019-04-24 10:42:43,749 [InstallationWorker] DEBUG SnowSoftware.Update.Data.RegistryManager [(null)] - Successfully set value UpdateRevision on key SOFTWARE\Snow Software\Snow Update Service\Installed Products\SnowLicenseManagerEnterpriseEdition to 401.
2019-04-24 10:42:43,750 [InstallationWorker] DEBUG SnowSoftware.Update.Product [(null)] - No previous license key, cannot reset the current one.
2019-04-24 10:42:44,160 [InstallationWorker] DEBUG SnowSoftware.Update.Product [(null)] - No previous license key, cannot reset the current one.
System.ApplicationException: Update could not be installed. Instructions have been rolled back. ---> System.Xml.XmlException: Root element is missing.
at System.Xml.XmlTextReaderImpl.Throw(Exception e)
at System.Xml.XmlTextReaderImpl.ParseDocumentContent()
at System.Xml.XmlReader.MoveToContent()
at System.Xml.Linq.XElement.Load(XmlReader reader, LoadOptions options)
at System.Xml.Linq.XElement.Load(String uri, LoadOptions options)
at SnowSoftware.Update.Installation.ExtendConfigurationInstruction.Execute(ProductUpdate update)
at SnowSoftware.Update.ProductUpdate.Install()
--- End of inner exception stack trace ---
at SnowSoftware.Update.ProductUpdate.Install()
at SnowSoftware.Update.ProductUpdate.Install(String temporaryPath)
2019-04-24 10:42:44,644 [InstallationWorker] DEBUG SnowSoftware.Update.Gui.Threading.InstallationWorker [(null)] - Installation not successfull, adding product 'SnowLicenseManagerEnterpriseEdition' to exclude list (for this installation cycle)

• Seen on Snow License Manager 9.0.0 upgrading to 9.1

• The Snow License Manager Event Store Service was corrupted somehow and couldn't be started.
• Tried to run the service through the command prompt and noticed that the assembly reference to Autofac.dll was wrong.
• Updated the service config with correct version.