Seaquel
SQL Server error code

SQL Server error 955

SQL Server raises error 955 at severity 14, which marks a problem with the query or data that you can correct.

Database %.*ls is enabled for Database Mirroring, but the database lacks quorum: the database cannot be opened. Check the partner and witness connections if configured.
Msg955
Severity14
Group0–999

Source: Database Engine events and errors