Hi Juliana Zhou,
Please refer to this article: https://www.c-sharpcorner.com/blogs/could-not-find-server-server-name-in-sysservers-in-sql-server
And this similar thread: https://learn.microsoft.com/en-us/answers/questions/817819/could-not-find-server-servernamehere-in-sys-server
Best regards,
Seeya
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