Seaquel
SQL Server error code

SQL Server error 9768

SQL Server raises error 9768 at severity 16, which marks a problem with the query or data that you can correct.

A database user associated with the secure conversation was dropped before credentials had been exchanged with the far endpoint. Avoid using DROP USER while conversations are being created.
Msg9768
Severity16
Group9000–9999

Source: Database Engine events and errors