Installation and server related problems

1. Steps to recreate the bug: Create a lesson page with tabs (shortcode from Guru theme on Wordpress) and insert H5P content into different tabs. This was all displaying perfectly until yesterday, and now nothing will display within tabs on Chrome or Firefox, but yes on Safari. When opening the Javascript console, there are no relevant errors and the H5P content will suddenly appear. Refresh the page and it disappears again! BTW inserting the content into a tabless part of the page works fine, but I've built my lessons using tabs and I would ideally like to keep doing so.

We've had some users report that they're seeing an unabletocopy error message when attempting to load, update, or edit existing H5P activities on their WordPress multisite (we're running Pressbooks, a plugin for WP multisite that turns the network into a tool to publish openly licensed web books).

Here's what we see when we open an H5P activity in the book in question:
 

When I go to open one of these activities, I see the following warnings/errors in the console:

I have installed H5P (current version) in Moodle Moodle 2.6.11.

The installation was carried out without problems, but when inserting an H5P activity and trying to access it from the course, the browser shows the following message: HTTP 500 error.

We have tried modifying the read and write permissions of the hvp folder and moodle data folders and still showing the same error.

We have tested with browsers: Chrome, Firefox and Edge.

Please, could you help us solve this situation?

Thank you.