Yeah, I've done all that. Everything works fine except Firefox. _._,_._,_

Did you try setting nvda back to factory defaults to see if that fixed the problem?
I am guessing you would of uninstalled nvda all together but did you also do the following area when the run command is run %appdata% then pressed the enter
key then found the nvda folder and either deleted it out all together then reinstalled nvda. .

Hi Jackie

 Is that the only place it is doing it saying unknown? do you get unknown spoken if down on the running applications area  when you arrow through them or are they spoken out correctly. any other weird stuff or just in fire fox?

Does nvda work in other browsers?

Did you try setting nvda back to factory defaults to see if that fixed the problem?

I am guessing you would of uninstalled nvda all together but did you also do the following area when the run command is run %appdata% then pressed the enter key then found the nvda folder and either deleted it out all together then reinstalled nvda. .

I also find at times if it is only in the browser a reset of it fixes the problem when things go weird in it.

I usually do this last.

The following page might help at https://malwaretips.com/blogs/reset-firefox-settings/

Reset Mozilla Firefox to default settings (Step-by-Step Guide)
If Firefox starts to act slow, crashes, or displays unwanted advertisements, resetting it to the default settings can help. The reset feature fixes many issues by restoring Firefox to its factory default state while saving your essential information like bookmarks and open tabs.
Resetting your browser settings will impact the settings below:
• Default search engine and saved search engines will be reset and to their original defaults.
• Homepage button will be hidden and the URL that you previously set will be removed.
• Default startup tabs will be cleared.
• New Tab page will be empty unless you have a version of Firefox with an extension that controls it. In that case, your page may be preserved.
• Pinned tabs will be unpinned.
• Content settings will be cleared and reset to their installation defaults.
• Cookies and site data will be cleared.
• Extensions and themes will be disabled.

Here’s how to reset Firefox to the default settings if you’re using a Windows computer:
1
Click the menu icon, then click on “Help”.
Click on Firefox’s main menu button, represented by three horizontal lines. When the drop-down menu appears, select the option labeled “Help“.
Click on the Firefox Menu button then select Help button
2
Click “Troubleshooting Information”.
From the Help menu, click on “Troubleshooting Information“.
Click on Troubleshooting Information button
3
Click on “Refresh Firefox”
Click the “Refresh Firefox” button in the upper-right corner of the “Troubleshooting Information” page.
Click on the Refresh Firefox button
4
Confirm.
To continue, click on the “Refresh Firefox” button in the new confirmation window that opens.
Click again on Refresh Firefox
5
Click “Finish”.
Firefox will close itself and will revert to its default settings. When it’s done, a window will list the information that was imported. Click on “Finish“.
Your old Firefox profile will be placed on your desktop in a folder named “Old Firefox Data“. If the reset didn’t fix your problem you can restore some of the information not saved by copying files to the new profile that was created. If you don’t need this folder any longer, you should delete it as it contains sensitive information.
That’s it your browser settings should be set to their original defaults. To check your computer

Brian - Windows 10, 64-Bit, Version 21H1, Build 19043  

I do not understand why some seek to separate a person from their actions.  The self is composed of an individual’s thoughts, actions, and expression, which are contained in and actuated by the body.  What you do and say is the clearest indicator of who you are.

      ~ Brian Vogel

It's working fine for me too with the current beta version of NVDA.

but NVDA does not recognize it, nor does narrator.