Install Readiness error when upgrading to ITMS 8.5 RU4:
CheckSSLSettingFeatureInIIS Failed to run
A specified logon session does not exist. It may already have been terminated. (Exception from: HRESULT: 0x80070520)
ITMS 8.5
Unknown - It appears that the Symantec Installation Manager was not able to successfully run the readiness checks against IIS.
Removed and reinstalled the IIS 6 Management Compatibility role, and then rebooted the Notification Server. The readiness checks then passed without failures, and we were able to successfully complete the upgrade to 8.5 RU4.