this may help you https://support.mozilla.org/en-US/kb/troubleshoot-and-diagnose-firefox-problems

OK so I did all steps (up to step 6), and after step 6 I was able to get the same result as in Chrome, which is:

https://i.imgur.com/18wLLsd.png

Log in to use your Facebook account with Twitter. Error Accessing App We're sorry, but the application you're trying to use doesn't exist or has been disabled.

This error occurs on both browsers, so it is likely that it is caused by something independent of each browser.

Hi jamesray1:

"Important: A recent update to the Facebook Platform Policies ended the ability to automatically post Tweets to your Facebook profile or page." <-- from https://help.twitter.com/en/managing-your-account/link-twitter-to-facebook

Therefore I don't think you can automatically post tweets to Facebook from any browser including Firefox and Chrome.

Cheers!

...Roland

Yes, I had already read that. However, I was confused because I thought that the article had a workaround for posting tweets automatically.

jamesray1 said

Yes, I had already read that. However, I was confused because I thought that the article had a workaround for posting tweets automatically.

Based on this tweet from August 2018 I am convinced it's not a firefox issue; it's facebook and twitter's support issue: https://twitter.com/TwitterSupport/status/1024758308081610753

Good luck! There's probably a 3rd party app or some such out there you can use!

...Roland

On a related note, this is an email from Wordpress:

Hello James,

We wanted to update you about an upcoming change Facebook is introducing to their platform, and which affects how you may share posts from your website to your Facebook account.

Starting August 1, 2018, third-party tools can no longer share posts automatically to Facebook Profiles. This includes Publicize, the WordPress.​com tool that connects your site to major social media platforms (like Twitter, LinkedIn, and Facebook).

Will this affect your ability to share content on Facebook? It depends. If you’ve connected a Facebook Profile to your site, then yes: Publicize will no longer be able to share your posts to Facebook. On the other hand, nothing will change if you keep a Facebook Page connected to your site -- all your content should still appear directly on Facebook via Publicize. (Not sure what the difference is between a Page and a Profile? Here’s Facebook’s explanation.) You can review and change your social sharing settings by heading to My Site(s) → Sharing on WordPress.com.

If you’ve previously connected a Facebook Profile to your WordPress.​com site and still want your Facebook followers to see your posts, you have two options. First, you could go the manual route: once you publish a new post, copy its URL and share the link in a new Facebook post. The other option is to convert your Facebook Profile to a Page. This might not be the right solution for everyone, but it’s something to consider if your website focuses on your business, organization, or brand.

While Facebook says it is introducing this change to improve their platform and prevent the misuse of personal profiles, we believe that eliminating cross-posting from WordPress is another step back in Facebook's support of the open web, especially since it affects people's ability to interact with their network (unless they're willing to pay for visibility) We know that this might cause a disruption in the way you and your Facebook followers interact, and if you’d like to share your concerns with Facebook, we urge you to head to their Help Community to speak out.