The solution was simple, but elusive.
1. Close Outlook.
2. Open Windows Explorer.
3. Tools > Folder Options > View; click "Show hidden files, folders, and drives."
4. Deselect "Hid protected operating system files (Recommended)" and click OK.
5. Navigate to %USERPROFILE%\AppData\Roaming\Microsoft\Protect.
6. Rename the folder S-1-5-21-
7. Rename the file CREDHIST to CREDHIST-old.
9. Launch Outlook, enter credentials when prompted, and click Save Password.