Hi there! I understand that Walling isn't displaying properly on your Firefox browser on your Mac with OS X 10.15. Let's work together to get this fixed.

Could you tell me a bit more about what exactly happens when you try to use Walling on Firefox? For example:

- Does the Walling website load but the content never shows?
- Do you get any error messages?
- Are you trying to use the Walling web app directly or the Walling browser extension on Firefox?
- Have you tried using Walling in any other browsers on your Mac? If yes, does it work there?

Knowing this will help me guide you precisely.

Meanwhile, here are some initial steps to try that often resolve display issues with web apps on Firefox:

1. Clear Firefox cache:
- Click the menu button (three lines) in the top right.
- Select Preferences (or Options).
- Go to Privacy & Security.
- Under Cookies and Site Data, click "Clear Data…" and clear cached web content.
- Restart Firefox and check Walling again.

2. Disable any conflicting extensions:
- Sometimes other add-ons may interfere. Go to the Add-ons Manager (via the menu).
- Disable all extensions temporarily.
- Restart Firefox and open Walling to test.

3. Check if you have the Walling Web Clipper extension installed and enabled:
- It won't affect the web app's display but can sometimes cause issues.
- You can find it here if you want to install it or verify: Walling Web Clipper for Firefox

4. Try accessing Walling in a Private Window:
- This disables most extensions and uses default settings.
- Use the menu > New Private Window and open Walling.

If none of these steps help, we can dive deeper, like checking specific Firefox settings or potential network issues.

Would you like me to guide you through any of those steps now? Also, please share any more details about the problem you see.

Let me know!