Testing this on a plain WordPress installation I cannot see the issue you are describing. Do you have the steps to reproduce this problem?
Note that this may be related to a browser extension or another third-party plugin on your WordPress site.
I am using H5P with Tutor LMS. When I published my h5p content sometimes I see a big H5P logo and blank page. I checked SHOW EMBED code and it worked. So I have gone through all my projects and checked the embed code box.
I tried with interective video and memeory game tools.
If you want to use the external embed feature while leaving the embed button hidden you need to set the following option in your wp-config.php:
define( 'H5P_EMBED_URL_ALWAYS_AVAILABLE', true );
But be aware that unless you have defined a CSP frame-ancestors header on your webserver somehow any site will be able to embed any of your content.
Thank you very much. It worked.