SQL Server Linked Servers not connecting
This is a common error in delegation permission for the linked server connection however you can fix it checking the Kerberos Connectivity or adding but none recommendable SQL Login ID in your Linked Server Connection.

You can find more details on how to use the Kerberos Connection Manager and add the delegation permissions on your AD based on this article. 
https://www.sqlshack.com/how-to-link-two-sql-server-instances-with-kerberos/

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