Troubleshooting credential validation

Table: Reasons for credential validation failure describes the reasons that validation can fail for an instance, replica, or instance group.

Table: Reasons for credential validation failure

Status code or error	Description	Explanation
40	Could not validate credentials. Failed to connect to client: <client>.	The host name is invalid.
46	The validation operation timed out waiting for a response from the client	You cannot connect to the host because the host is down.
41	Validation of operating system user/password failed for client: <client>.	The host name is correct, but the user name or password is invalid. The credentials use have the setting Use these specific credentials, but the user account does not have the required the local security privileges Impersonate a client after authentication and Replace a process level token. See Configuring local security privileges for SQL Server.
1939	The specified user does not have SQL Server System Administrator privileges.	The credentials do not have the "sysadmin" role and the validation fails.
Invalid configuration detected.	Invalid configuration detected. The service user for the NetBackup Client and NetBackup Legacy Network services must be the same user. Change the service users in the Windows Service Manager and try again.	The NetBackup Client Service or the NetBackup Legacy Network Service requires but does not use the same user for the logon account. See Configuring the services for SQL Server backups and restores.