This is the human-readable error text accompanying fsmRmtInvErrCode for the last remote call this provider's FSM made to vCenter. For this specific object it's the quickest way to get an actual root-cause string, e.g. an authentication or SSL trust failure message, for a failing vCenter registration without needing vCenter-side log access. A value like 'Cannot complete login due to an incorrect user name or password' immediately tells you the fix is on the vCenter service-account credentials configured for this provider, not a network issue.