For one reason or another, the external DB had some sort of issue where an SQL repair had to be initiated on the DB.
You can further determine this is the case as the following ZVM log will be present mentioning invalid credentials, yet the credentials can be used to login to the External DB from the ZVM:
2020-02-17 12:40:47.1464,E,13,Zerto.Zvm.Configuration.Core.Notification.NotificationBus,AddError,Configuration Engine Failed to verify,"System.Data.SqlClient.SqlException Boolean TryGetConnection(System.Data.Common.DbConnection, UInt32, Boolean, Boolean, System.Data.Common.DbConnectionOptions, System.Data.ProviderBase.DbConnectionInternal ByRef) System.Data.SqlClient.SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) ---> System.ComponentModel.Win32Exception (0x80004005): The user name or password is incorrect
ZVM upgrade validation fails for the following errors:
Additionally, the ZVM DB is external.
Ensure the DB service user account is included in the local administrator group. If not present, add it in and try the upgrade again.
If the above does not provide relief, run an SQL repair operation. Then, try the upgrade again.