Hi, it appears that ACF Widgets 5+ is incompatible with WordPress Popular Posts. Here’s a discussion with the developer of WPP about it, who says the reason it’s incompatible is more to do with how ACF Widget’s works. Any thoughts on this?
I ended up fixing this by simply using the ‘acfw_should_register_widget_in_acfw_widget_factory’ filter, and checking if the $widget_class name included ‘wordpressPopularPosts’, since the WPP widget class contains that name. Everything works perfect with that in place.