Here is the last reply: Hey there JB, I wanted to thank you for waiting I was able to see that we are working with the list Laura Letchinger Art Email List and adding the popup form to the site https://www.lauraletchingerart.com/template-3/. While I have not come across your exact situation previously I am glad to look into this topic further for you.
Looking over your site I was able to see that you have put in the MailChimp form. I was able to copy it from your source code after viewing it and run it in https://jsbin.com which is a free HTML runner you can use. From here my test email was able to join the list.
I was also able to inspect the page and see that you have errors (https://cl.ly/2Y3o3X1T030V ) that will need to be addressed with an IT proffessional or an expert partnered with MailChimp at experts.mailchimp.com.
While we are experts in looking at the source code we are not trained in advance HTML coding here at MailChimp support and this is why you will want to reach out to an expert to make sure the site does not have these alerts.
https://cl.ly/2Y3o3X1T030V
I am not familiar with CoverPlug and would have to look for more information pertaining to it.