@jakeyjake88 I believe the problem is due to the fact that the Ninja Forms plugin is looking to load a script (usually JavaScript) and you have not properly enabled JavaScript to load on your site.
I inspected your popup using Google Chrome Developer tools. The following markup was found within the popup itself:
<noscript class="ninja-forms-no-script-message">Notice: JavaScript is required for this content.</noscript>
<div id="nf-form-cont-2" class="nf-form-cont">
<div class="nf-loading-spinner"></div>
</div>
Do you see the class attribute ‘nf-loading-spinner’? That’s the effect being rendered by Ninja Forms because a JavaScript script cannot execute on your site.
I don’t know whether the issue is being generated by a conflicting plugin, or your active theme (Auberge by WordPress). The best way to isolate the issue is to test the site in a local development environment (so your live site is not impacted).
Turn off all plugins except NF and Popup Maker. See if the issue still occurs with just this minimalist setup. If the issue resolves, then you know it’s a conflicting plugin. Reactivate plugins one at a time until the problem reappears. Then you’ve isolated the plugin.
If the problem persists after testing plugins, switch to a default WP theme (e.g. Twenty Seventeen) and see if the problem will resolve. If a change in theme fixes the problem, then it’s an issue with your current theme. In that case, contact the theme author for support.
If neither switching off plugins or changing themes fix the problem, write back. We’ll have to think of next steps.
Hope this helps. The truffles BTW sound extremely yummy. Both the plugin author and myself are foodies, and appreciate delicious food.
Cheers!