LAN servers have never recognized admin/superadmin status from the serverprefs.cs file, as there isn't a GUID associated with LAN connections (only exclusion would be an alternative authentication system like TCMS, etc).
Use the AdminHUD or SAD() console function to login as a superadmin...
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Also in the console type: youclientid.isadmin=1; AND youclientid.issuperadmin=1;
Use the AdminHUD or SAD() console function to login as a superadmin...