human verification is not working

[pnhltt]

We've had to deal with a lot of spam registrations recently. Kept checking the settings, all the boxes were ticked in the right places. One of the new members pointed out yesterday that he wasn't prompted to type in what was on the picture or similar at the time of registration. Tested it and found that image verification, Q&A verification or reCAPTCHA verification do not work at the point of registration. Checked all the settings in the adminCP, changed settings to alternative ones (cycled through 3 kinds of verifications), still no change at registration. We definitely had it working up until several weeks ago, but can't pinpoint when things changed. We upgraded the forum in April, might have happened then.

Any help would be appreciated. The forum runs on 4.1.3.
Thanks.