I have followed the instruction.
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Here is the reply from Mailchimp team:
Thank you for getting back to me with this information. I was able to run a test on my end using my iPhone 7 and I did replicate the behavior where the pop up appeared, however the was not a place to input the email address.
For my next troubleshooting step, I took a look at how the coding for the pop up form and how it was placed on the website. In reviewing this, we did notice something was a little off. It seems to be a conflict with the popup form and the website theme. Below I have a screenshot of the bit of code that I am referring to.
Screenshot:(Please refer to attached file)
Basically, it's showing that if the page is too thin, the fields will disappear from the HTML and it looks like the banner on the actual website is overriding the field that should be on the form
For this, you would need to edit the code in order for this to work as intended. A thing to know here is if their store is hosted on something like BigCommerce or Shopify, you may might have to hire a dev or choose a new theme. Just to note, with MailChimp, us support agents are experts in the behavior of the app itself, however, we rare not trained in custom coding, which limits the amount of support I can offer for this issue. My suggestion here would be to reach out to a developer or someone that is comfortable with custom coding on your end to further assistance.
Kindly help me on this as I am losing subscribers daily and the issue has persisted for too long. Thanks a lot.