VxRail manager utilizes the PTAgent running on the ESXi hosts as part of a VxRail cluster in order to pull hardware related information from the host. If you are experiencing host visibility issues in VxRail manager, then a good starting point is to check the PTAgent status,
PTAgent is bundled with VxRail code releases as part of the Dell PowerEdge components. ESXCLI can be used to determine the PTAgent version running on the host.
esxcli software vib list | grep dellptagent