ServiceDesk 8.x install failed and rolled back the changes. Now when trying to access Process Manager portal it no longer opens, not even showing the login page.
ServiceDesk Setup rollback removes Symantec.ServiceDesk.Im.Core.dll and Symantec.ServiceDesk.Cm.Core.dll from Workflow\Shared\customlib folder. These libraries contain Change Management and Incident Management data types used by other libraries - notably Automation libraries.
This issue is fixed in ServiceDesk 8.5 RU1.
If you have correct enough versions (at least the same major version as the one you attempted the upgrade to) of Symantec.ServiceDesk.Im.Core.dll and Symantec.ServiceDesk.Cm.Core.dll libraries available - for example in a backup made before upgrade attempt - place these into %ProgramFiles%\Symantec\Workflow\Shared\customlib folder.
Alternatively, remove *.Automation.*.dll from %ProgramFiles%\Symantec\Workflow\ProcessManager\Plugins\Rules