It’s not uncommon to see questions on StackOverflow relating to SQL Server connectivity issues. Microsoft support have published the following guide to help troubleshoot connectivity issues:
Solving Connectivity errors to SQL Server
In addition to providing a checklist of items that you can go through, it provides step by step troubleshooting procedures for the following error messages:
- A network-related or instance-specific error occurred while establishing a connection to SQL Server
- No connection could be made because the target machine actively refused it
- SQL Server does not exist or access denied
- PivotTable Operation Failed: We cannot locate a server to load the workbook Data Model
- Cannot generate SSPI context
- Login failed for user
- Timeout Expired
- The timeout period elapsed prior to obtaining a connection from the pool
There are also troubleshooting guides for Always On and SQL Azure DB connectivity issues:
Troubleshooting Always On Issues
Troubleshooting connectivity issues with Microsoft Azure SQL Database