I think I fixed it. Was a plugin conflict. Seems like a lot of the site speed/optimization plugins conflict a bit with the reply box. My specific issue was with async javascript. I put add a script exception to make it work

Hey, I've narrowed the issue down to a conflict between Flatsome, WpForo and Thrive. When all three are active, the issue kicks in. If I disable one of them, the issue disappears. Any thoughts on next steps? Best, A P.s., I'd rather not hand out admin access. You should be able to recreate the issue on your own staging environments.

Ok - I used a staging environment to narrow the issue down to a conflict between any of the Thrive plugins (Thrive Ultimatum, Thrive Leads, Thrive Quiz Builder) and WpForo. Activating ANY Thrive plugins causes the "Please Insert Required Fields!" error when adding a new topic. Disabling ALL Thrive plugins is the only way to get adding topics working again. What's the next step here? Do I need to take this up with Thrive's developers? Or will you? If it's nerfing my site, it'll be nerfing other installations. Thanks for your help, Robert! Best, A P.s., ...

Hi @shl, Sorry for the late response. Please make sure you use the latest wpForo version. This also may be a conflict with other plugins. It's better to deactivate all plugins and test it again. Then activate plugins one by, test it one by one after each plugin activation and find the conflict maker.

@beyondforce, Do you have any idea why is it happing? Is it because of another plugin that causes this conflict? Yes, this is a plugin conflict for sure. I'm sorry, but I cannot point you the plugin that caused this CSS issue.   

Hi @lmarak, You don't need any addon for the text editor. It comes with free core plugin. Can you leave a screenshot of your editor? If you don't see it then you have plugin conflict. In most cases it's conflict with optimizer and cache plugins. Please disable those or just exclude forum page from those, delete all caches and check again.

There is no any file that should be edited for this conflict. This is a conflict with your theme or with some plugin. Please leave your forum URL, we'll find a time to register and check CSS conflicts on your website.