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Issue to SQL server 2012

Peter_1985 2,586 Reputation points
2021-02-22T07:16:39.973+00:00

Hi,
There was no change to SQL server 2012 but why did the issue below arise?

TITLE: Connect to Server

Cannot connect to WIN-429I3QNHOQT\EXPR2012.

ADDITIONAL INFORMATION:

A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) (Microsoft SQL Server, Error: -1)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft%20SQL%20Server&EvtSrc=MSSQLServer&EvtID=-1&LinkId=20476

BUTTONS:

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Accepted answer
  1. CathyJi-MSFT 21,131 Reputation points Microsoft Vendor
    2021-02-23T05:54:17.147+00:00

    Hi @Peter_1985 ,

    Please follow below steps to troubleshot the issue,

    1. Make sure SQL Server Service is running
    2. If a named instance, make sure SQL Server browser service is running. Make sure the instance name is spelled correct and there is actually such an instance on your target machine.
    3. If this is remote connection. Please make sure SQL Server is configured to allow remote connections and you have enabled TCP\IP protocol
    4. Examine the SQL Server error log for messages confirming that SQL is listening on the expected network interfaces and ports
    5. Test server connectivity with PING from the client machine
    6. Test port connectivity using TELNET to the server and port (from step 4) from the client machine. For example
      TELNET <server-name> 1433
    7. Check firewall settings if step 5 or 6 connectivity test fails. Configure the firewall on the server instance of SQL Server to open ports for SQL Server and the SQL Server Browser port (UDP 1434).

    If you have some confuse about the steps, please refer to Resolving could not open a connection to SQL Server errors to get more information.

    If it is not work, please let us know .

    If the response is helpful, please click "Accept Answer" and upvote it, thank you.

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  1. Tom Phillips 17,721 Reputation points
    2021-02-22T14:50:22.307+00:00

    That is a generic "could not connect to server" message and does not help diagnose the actual problem in any way.

    I suggest you start here:
    https://learn.microsoft.com/en-us/sql/database-engine/configure-windows/troubleshoot-connecting-to-the-sql-server-database-engine?view=sql-server-ver15

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