WordPress not allowing comments, says "empty message"

Try deactivating all plugins. If that resolves the issue, reactivate each one individually until you find the cause.

If that does not resolve the issue, try switching to the Twenty Fourteen theme to rule-out a theme-specific issue (theme functions can interfere like plugins).

Thank you! I’ve already deactivated one I just added today and thought I had fixed the problem (it let me post) but all my testers are still getting the error message. So I’ll try deactivating the rest.

Excellent, please let us know how it goes. ??

I deactivated most plug-ins,and comments are working again. Now I need to reactivate the few I really use and test again.

Yep, if you don’t have too many it’s better just re-activate them one-by-one, testing each time. That way you’re sure to catch the one causing the problem.