Mathematica fails to load welcome screen: "Authentication Required"

Problem

When I open Mathematica 12.1.0 on windows 10, I get an "Authentication Required" window during the splash screen. The auth window has no input or buttons, and the text in the window is:

    FormControl[Null,
    FormObject[{Username-><|Interpreter->String, Label->Username,
        Control->(AuthenticationDialogDump`formField[##1, BoxID->
            AuthenticationDialogDump`$AuthenticationBoxID]&),
        Input->|>, Password-><|Interpreter->String, Label->Password,
        Control->(AuthenticationDialogDump`formField[##1, BoxID->
            AuthenticationDialogDump`$AuthenticationBoxID,
            FieldMasked->True]&),
        Input->|>},AppearanceRules->Automatic]]

I believe (but cannot prove) that this is a result of me creating and partially completing a database connection with the DatabaseLink package.

I cannot actually interact with Mathematica, because the program crashes/closes when I close the authentication window. The welcome screen is never displayed.

Does anyone know how to fix this?

Attempted solutions so far

• Reinstall the program
  • Error persists
• Deleted an .m file in %appdata% which contained an OpenSQLConnection command corresponding to my partial database link
  • Error persists
• Searched registry for entries related to my database link
  • Nothing found
• Searched the entire hard drive for any .m files modified since the last time I successfully opened mathematica
  • Nothing found