tinkererguy

I should add that I’m talking about Really Simple Captcha, and some sort of issue interacting with it on my contact form.
https://contactform7.com/captcha/

See also related post here:
https://petermolnar.eu/open-source/wordpress/wp-ffpc/#comment-998190516

Got great clarification that I’d like to share, since my post above implies the very presence of jquery broke things, and that’s not the case:

…plugins that use jQuery are not by definition incompatible with Fancybox for WordPress, the problem arises only when a plugin loads jQuery on it’s own instead of using WordPress functions to do it, causing jQuery to load twice and break things…

Found the culprit.
I went into my site’s filesystem, sorting the /plugins directory by date of folder creation, narrowing it down to only 2 recently installed plugins.

“WordPress Table of Contents Plugin” version 1.1:
https://rastider.com/wordpress-table-of-contents-plugin
is apparently incompatible with FancyBox, yep, it uses jquery (see above site for details).

As soon as I deactivated WordPress Table of Contents, making no other changes at all, FancyBox 3.0.1 immediately began working just fine again.

Hmm, “Revert to defaults” didn’t work, deactivating, uninstalling, going back to 2.7.5 didn’t work. Then deactivated, uninstalled, then went to 3.0.1 again, that didn’t didn’t work, I’m outta luck. Hoping for a fix, perhaps 3.0.2 is coming soon? Any known conflicts with other Plugins? I don’t have any other Plugins installed that use jQuery.

3.0.1 was working (after resetting to defaults) for about a week, on WordPress 3.3, but it’s now failed again. Can’t find any other conflicting Plugin that could explain this.

Unfortunately, this time, resetting to defaults didn’t help. Deactivating, Deleting, then Adding, then Activating the plugin again didn’t help either.

Sounds like going back to 2.7.5 is the way to handle the wait until a fix is found.