It does not appear the box text in Firefox

[MarkFL]

First, let's try disabling the plugins and see if this resolves the reported issue.

Follow:

AdminCP -> Settings -> Options -> Plugin/Hook System

And set "Enable Plugin/Hook System" to "No" then click "Save".

Try posting a reply and see if the editor now shows up. If the editor is present, then re-enable plugins and try disabling your add-ons one at a time until you find the add-on causing the problem. Let us know the add-on causing the conflict, and we can go from there.

If the editor is still not present after disabling the plugins, then let us know and we can go from there by checking your templates.