Embedding from Wordpress H5P not showing on other sites
I've recently started using H5P and have created a few activities on my Wordpress site, however, I'm having difficulty getting it to embed on other websites. For example, if I copy the embed code and paste it into a blog post on my own site it works fine. However when I copy the embed code and say paste it into Teachable and Thinkific (LMSs), I see a grey box representing the iframe but it says it wasn't able to connect to my site.
I've read that the issue could be to do with mixed content http and https, however my site has a SSL Certificate installed and so starts with https as do the sites I'm trying to embed content on. Here's an example of the embed code from a test activity I've created, I'd really appreciate any guidance on how to get this to embed on other sites.
<iframe src="https://www.vuesolutions.co.uk/wp-admin/admin-ajax.php?action=h5p_embed&..." width="759" height="611" frameborder="0" allowfullscreen="allowfullscreen"></iframe><script src="https://www.vuesolutions.co.uk/wp-content/plugins/h5p/h5p-php-library/js..." charset="UTF-8"></script>
Thanks in advance.
P.s. I'm creating the content on my own site rather than on H5P.org to keep it private.