Spellcheck has stopped working in my c5 site. The functionality in both clicking the spellcheck button in the WYSIWYG editor, and the native browser spell checking (red underlining) is no longer working inside of the editor window.

In the attached picture, you'll see the browser spell check is working in the simple text box, but not in the WYSIWYG text box.

I am running an older version of c5 (5.5.2.1)... Is this why? Anything I can do to fix?

Thanks.