Name	Description
agentOutOfDate	*Since*
agentUpgrade
insufficientLicenses
licenseExpired
passwordDecryptFailure	*Since*
sslThumbprintVerifyFailed
unknown	*Since*
userRequest
vcVRAMCapacityExceeded	*Since*

         <simpleType xmlns="http://www.w3.org/2001/XMLSchema" xmlns:vsan="urn:vsan" name="HostDisconnectedEventReasonCode">
            <restriction base="xsd:string">
               <enumeration value="sslThumbprintVerifyFailed"/>
               <enumeration value="licenseExpired"/>
               <enumeration value="agentUpgrade"/>
               <enumeration value="userRequest"/>
               <enumeration value="insufficientLicenses"/>
               <enumeration value="agentOutOfDate"/>
               <enumeration value="passwordDecryptFailure"/>
               <enumeration value="unknown"/>
               <enumeration value="vcVRAMCapacityExceeded"/>
            </restriction>
         </simpleType>

Enum - HostDisconnectedEventReasonCode(vim.event.HostDisconnectedEvent.ReasonCode)

Enum Description