Remote Execution server failed to perform default gathering with error : The following error occurred before the main processing of the given gathering: [DBNETLIB][ConnectionOpen(Connect()).]SQL Server does not exist or access denied.
The SQL server might be using TCP dynamic ports or listening on a non standard port (1433).
When you specify the connection to SQL server in the remote execution without putting any port number, it will use the standard port 1433 to connect to the SQL server.
Even if you have specified the port, you might not be able to get connected once the SQL services get restarted if TCP dynamic ports are used.
Go to SQL server configuration Manager and change the corresponding IP address to listen on TCP port 1433.
How to change it to listen on TCP port 1433?
1. Go to SQL server configuration Manager
2. Expand "SQL Server 2005 Configuration"
3. Select Protocol for MSSQLSERVER (Your SQL Instance)
4. Properties on TCP/IP
5. Click on IP Addresses tab
6. Make sure the TCP dynamic ports for the corresponding IP address is cleared
7. Type 1433 on the TCP port for the corresponding address