When installing service deployments such as Guest Introspection through NSX Manager the installation fails. The host task displays error Cannot complete the operation. See the event log for details.
The event log displays error event.com.vmware.vim.eam.issue.vibNotInstalled.fullFormat.
The service deployment shows the error Agent VIB module cannot be detected on the host. This may be due to a pending reboot on the host due to an earlier operation. Please check for any errors on the vCenter console of host that may be causing this. Resolving this error will attempt to install the VIB on the host again.
If an instance of Update Manager is registered with the same vCenter Server as NSX Manager then Update Manager must be fully functional. When Update Manager is present it is relied upon by NSX Manager to approve the install or uninstall or vibs. Resolve the issue with Update Manager, or uninstall Update Manager.
Once Update Manager is removed or repaired to a working state the service deployments will install successfully. This VMware KB confirms the issue occurs when Update Manager is unavailable and advises that modules are manually installed instead, however it is not clear in stating that the service deployments succeed without Update Manager, and therefore the UM instance can be removed as a work around.