The reason why this happens is because you are either using some third party caching system which is doing exactly what it is supposed to do: caching your content to allow your site to run faster or you haven't cleared your
Just clear your site cache once to ensure the latest changes made on your Magento store are being recognized by Magento's cache mechanism. Once the cache is fully purged you should straightway see the PushAssist subscription opt-in on your front-end site.
If you are using reverse-proxy content sites like Cloudflare, Incapsula etc. Just clear the cache from their console for once.
Finally, clear your browser cache and refresh your page to see subscription opt-in dialog appearing for you and your customers. If it is still not showing up, you may want to consider contacting support at firstname.lastname@example.org.