Hi there,
thank you for reaching out regarding this issue. Can you please confirm that you have our plugin version 4.5.4 installed (you can find the version when you go to the list of all your plugins.
I just tested that version on a brand new WordPress site and got it to work, which leads me to believe that you may have either a security plugin that prevents the Riddle plugin from working on another plugin that creates a conflict with the Riddle plugin.
If you got the latest version of our plugin, there are 2 things you can do:
1) use the Riddle embed code without the plugin. Here is how: https://www.riddle.com/docs/creators/adding-a-quiz-to-a-gutenberg-block/
(note our leaderboard will not work without the plugin)
2) install the health check plugin: https://www.ads-software.com/plugins/health-check/ and use that to temporarily disable all other plugins except for Riddle. If the Riddle plugin works, enable the other plugins one by one to find the one that is causing the conflict. If you identify that one, let us know, so we can install that on our end and try to fix the incompatibility.
Also, please reach out to us using the chat function on riddle.com. That way we can help real time with any issue with our tools