Manual switch or unswitch of an O365 mailbox causes the following error to occur in the MMEX console:
"Failed to (Un)Switch user. Interface not registered (Exception from HRESULT: 0x80040155)"
Additionally the console log (EMWMigration.log) will contain the following error:
The following DLL is either missing or not registered on the machine where the MMEX console is installed:
%ProgramFiles(x86)%\Quest Software\Migration Manager\Active Directory\Directory Migration\QsDirectoryMigrationEngine.dll
If the DLL exists in the correct location, register it using Regsvr32.
If the DLL doesn't exist it means the AD components for O365 migration are missing from the console. Install them from the Migration Manager installer. The required component is found under "Migration Manager | Migration Manager for Active Directory | Migration to Office 365"