Seaquel
SQL Server error code

SQL Server error 504

SQL Server raises error 504 at severity 16, which marks a problem with the query or data that you can correct.

Unable to connect to debugger on %ls (Error = 0x%08x). Ensure that client-side components, such as SQLDBREG.EXE, are installed and registered on %.*ls. Debugging disabled for connection %d.
Msg504
Severity16
Group0–999

Source: Database Engine events and errors