"A network-related or instance-specific error occurred while establishing a connection to SQL Server ..."

Test Connection fails for a Microsoft SQL Server Database Account Domain in the Enterprise Credential Vault (crdvlt)
Configuring Microsoft SQL Server Database Password Checkout
The following error appears as the Status after selecting Test Connection:
[unixODBC][Microsoft][ODBC Driver 11 for SQL Server]A network-related or instance-specific error has occurred while establishing a connection to SQL Server. Server is not found or not accessible. Check if instance name is correct and if SQL Server is configured to allow remote connections.

Please verify the server address and port are defined correctly in the odbc.ini file and that it is accessible from the involved Manager server. It is possible for there to be a network communication problem (software or hardware firewall, etc.) or perhaps even a DNS issue.

Also, verify the syntax of the odbc.ini file, please refer to the following:
TID 7021177 - odbc.ini Connection String Keywords (unixODBC)
Note: The port may not be an attribute and may be defined in the Server keyword.

The specified server cannot be found or is not accessible.