When submitting a comment, Wordpress returns 0?

Question

WordPress

Nothing has changed, even compared the files with github, when adding a comment, ajax-admin.php returns 0. The
question is how can I get a more detailed error?
Or perhaps this is a common case, a day ago everything worked.
The most interesting spam if you remove the approval manually comes...

Answer 1

0 means that the handler function of the sent action was not found. what value of action is sent?