executing form requires access to wp-admin

I recently added a layer of security to my site, requiring authentication , via .htaccess and .htpasswd, for any user wishing to access the wp-admin directory. This, however, has broken the Mailchimp signup form, which now requests that authentication after the user clicks on the mailchimp form button to sign up.

So, I have to find out if there is something to be done to avoid this issue, while maintaining the authentication for access to wp-admin, or if I have to find a different method for getting my users to sign up to the mailchimp list.

Thanks in advance.

https://ww.wp.xz.cn/plugins/yikes-inc-easy-mailchimp-extender/