Hi, 

Please find below the way to the problem :

1. Add a database activity
2. Create a field 'Textarea field"
3. Be sure to use Atto editor
4. Add entry
5. Try to add a h5p content (button H5P on Atto editor)
6. The pop up don't alllow you to see the content bank

I've done this test with the capabilities :

• atto/h5p:addembed
• moodle/h5p:deploy
• moodle/h5p:setdisplayoptions