As a Firefox support forum contributor, I can provide some guidance regarding the issue you're experiencing with Facebook messages in Firefox. It seems that you're encountering a problem where you are unable to reply to messages on Facebook while using Firefox as your default browser. This issue has been reported by several users, and you're looking for a solution. Here are a few steps you can try to troubleshoot and potentially resolve the issue: Clear your browser cache and cookies: Sometimes, stored data can cause conflicts or issues with certain websites. Clearing your browser cache and cookies can help refresh the browser and resolve any temporary glitches. Disable browser extensions: Some browser extensions or add-ons may interfere with the functionality of certain websites. Try disabling any extensions you have installed in Firefox and see if that resolves the problem. Update Firefox to the latest version: Keeping your browser up to date ensures that you have the latest bug fixes and improvements. Check for updates in the Firefox menu and install any available updates. Try using Firefox in Safe Mode: Safe Mode allows you to troubleshoot Firefox with all extensions and custom settings disabled. Launch Firefox in Safe Mode and see if you can reply to Facebook messages without any issues. If none of these steps resolve the problem, it might be helpful to gather more information about your specific setup. Are you using any specific versions of Facebook or any other relevant details? This information can help us further investigate the issue and provide more tailored assistance. I hope this helps, and please let me know if you have any further questions or if any of these steps resolve the issue for you.