Hello,
Thank you for your kind answer. I’d be happy to get the pro version, but your statement “products that contain all searching words will have higher priority and will be visible at the top of search results” doesn’t seem to be true in my case as I wrote in my original post. Unless this is a setting I didn’t find. I’d send you my URL to see, but I don’t want it to be public.
@matwin23 seems my issue got resolved, as I understand it the most recent WCFM update caused an error, which was registered by the Wordfence plugin as a security issue (even though Wordfence was installed on a different WordPress but on the same TLD) and blocked some code. Disabling Wordfence for the time being and rolling back to an earlier WCFM version should fix the issue.