I had SQL Server 2019 Developer Edition installed and working correctly. Could access via SSMS without issue. About a month ago, I lost connection. Tried checking everything I could find online, no luck. Reinstalled version 19, and even tried version 22, still no luck. Had IT reformat the PC and do a fresh install of 19. Still no luck. Get this message every time:

Internal connection fatal error. Error state: 15, Token : 23 (Microsoft.Data.SqlClient)

On a side note, I ran the same 2019 installer on an old non-employer PC and it lets me connect via SSMS without issue. Seems like a work PC related issue.

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Instance is on the same computer that I am trying to log in from. I get the error when I open SSMS and try to connect with windows authentication.

I tired connecting with the authentication type (SQL server authentication), using login: (sa) and password (sa). I get the same error message. Our IT team also tried logging in with their account, same message.

Within SQL Server configuration manager/Sql Server Services/SQL Server(MSSQLServer) the server is indeed running. Under Protocols, only shared memory is enabled. Shared memory is the only protocol enabled on the PC where SSMS lets me in.

  • 1
    When people ask for clarification or more detail, it is best to add it to the question body (in a natural way). Adding comments makes your question harder to understand and does not bump the question on the home page for new views. I have added your comments to the question on this occasion.
    – Paul White
    Dec 6, 2023 at 22:25
  • How have you verified the SQL Server Instance is running? Have you checked the service? SQL Configuration manager that all protocols enabled?
    – betelgeuce
    Dec 7, 2023 at 11:37

1 Answer 1


Some people seem to report this is an issue with specific updates of .NET on Windows. Does your computer have this KB5011048 installed?

Please see this potentially related DBA.StackExchange.com answer:

Encountered the same issue but it is gone since I uninstalled windows update KB5011048

  • I have KB5001716 ( installed on the PC having the issue. I just checked on the PC not having the issue (my home pc) it also only has KB5001716 installed. It was worth checking! but doesn't to be related to the installed KB version
    – jsp
    Dec 6, 2023 at 20:53
  • @jsp I'm not an expert on how Microsoft structures their updates, but I believe one KB can contain changes of another earlier KB too. It seems KB5001716 was released after KB5011048, and is relatively recent (early October of this year). Might be worth triple checking, or trying to rollback or update forward (if there's a newer one) on your problematic PC anyway, with lack of any other options.
    – J.D.
    Dec 6, 2023 at 21:03
  • 1
    Understood! I will start looking into testing roll forward and backward tests. Its worth a shot!
    – jsp
    Dec 6, 2023 at 21:06

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