SQL Server has the ability to enforce the use of a security connection from the client to the server via the use of certificates and encrypted transport. In some environments administrators are disabling the use of SSL and TLS1.0 and restricting access to either via TLS1.1 or TLS1.2.
In an environment where SQL Server is using a secure transport and the administrator has disabled SSL and TLS1.0 the RockSolidAgent may not be able to connect to the SQL Server instance. In the RockSolid console the instance is showing as down even though all connection details are correct and the necessary RockSolidAgent security account permissions are granted.
The RockSolidAgent is written in Microsoft .NET and uses the Microsoft .NET ADO.NET SQLClient as the primary means of transport communication between itself and the target SQL Server instance(s). In order for RockSolid to connect to the secured SQL Server instance, the Microsoft .NET installation has to first be patched to ensure it supports the TLS configuration of the target host.
To do this see the following link from Microsoft:
Scroll to the section "Client component downloads" and apply the relevant client components to upgrade the .NET version being used by your RockSolidAgent installation.