Hi Charles,
May I know where did you paste the code we provided to you? I checked your website source code and the header of the website didn’t got messed up by our css code.
May be you pasted the code at wrong place, which broke the header. We pasted the same code at the required place and the checkboxes started working on your website.
I request you to please confirm it with your developer. And let me know regarding the same.
Regards,
Kriti