Error: "Failed to connect to the SQL Server using all possible protocols"
Agent is protected and backed up properly. However SQL instance(s) in agent's Summary tab are shown with the yellow mark and error: "Failed to connect to the SQL Server using all possible protocols"
Issue is caused by missing registration of MS SQL CLR components on the agent server.
To resolve the issue, please perform a repair of SQL installation on the agent server using SQL installation media. Necessary CLR components along with other actions will be performed. Please restart the Rapid Recovery agent service after the repair and either wait or perform metadata refresh from the Core console (hover mouse over the agent name until "..." will be shown next to it, click on ... and select Refresh Metadata).
Please note that even though backups are taken properly, when SQL instance is shown in yellow state, it means that SQL VSS Writer will not be called and databases will no be backed up in their consistent state. It's highly recommended to troubleshoot and resolve the yellow status of SQL instances.