How do I fix the SQL connection errors?
For more information, see Viewing the SQL Server error log.
Step 1：Verify that the instance is running.
Step 2: Verify that the SQL Server Browser service is running.
Step 3: Verify the server name in the connection string.
Step 4: Verify the aliases on the client machines.
Step 5: Verify the firewall configuration.
Hope this helps
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