Improved Popup Message For Blocked Self-requests Due to Firewall, HTTP Auth, Etc

When the self-requests for optimization are being blocked by a user's server due to firewall setting, HTTP authentication, security plugin, or something similar, Imagify Tools shows something like this (though the error codes can also be 401 or 403):

We could offer a popup informing users this is the cause and linking to possible solutions:

The code below links to the same Optimization is Stuck page as we do for cURL Error 28 / timeout issues, and we could add a section to it specifically for these cases with suggestions like:

• Whitelist 51.68.166.142 with the server or possibly security plugins

• Use the following in wp-config.php if site is behind HTTP authentication:

define( 'IMAGIFY_AUTH_USER', 'your_auth_username_here' );
define( 'IMAGIFY_AUTH_PASSWORD', 'your_auth_password_here' );

• Disable security plugin

Or we could create a new page with these suggestions, whatever the team thinks is the best option.

<div id="swal2-content" class="swal2-content" style="display: block;">A firewall, server setting, HTTP Authentication, or security plugin is preventing image optimization. <a href="https://imagify.io/documentation/optimization-is-stuck/" rel="noopener" target="_blank">More info and possible solutions</a>.</div>

Start by locating the Imagify Tools handling for blocked self-requests and the existing cURL Error 28/timeout popup. Confirm how HTTP 401, 403, and firewall-related failures are surfaced, then update the popup and the Optimization is Stuck documentation with the agreed guidance; done means affected users see the explanatory message and a working help link.