Hmm, for me, that address does a weird thing in Firefox 90 where it makes the current window very small -- shrinks it to the size of a small dialog. Are you running Firefox 90 currently?

If your goal in resetting the Primary Password is to clear your saved logins and start fresh, you also could do that by deleting a pair of files.

You can rename/remove logins.json and key4.db in the Firefox profile folder with Firefox closed to reset the Primary Password.

• https://support.mozilla.org/en-US/kb/reset-your-primary-password-if-youve-forgotten-it

You can use the button on the "Help -> More Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> More Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

Note that you can also run this code in the Browser Console.

• javascript:void(openDialog("chrome://pippki/content/resetpassword.xhtml","_blank","chrome,titlebar",window))
• "3-bar" menu button -> Web Developer or Tools -> Browser Tools -> Web Developer Tools
• https://developer.mozilla.org/en-US/docs/Tools/Browser_Console

To enable the command line in the Console:

• select "Enable browser chrome and add-on debugging toolboxes" in the Web Developer Tools settings
• https://developer.mozilla.org/en-US/docs/Tools/Settings