Details from the OP:

"A web accessibility audit on our Moodle course revealed two areas where the accordion controls do not comply with WCAG: content is not keyboard accessible and expanding controls do not have appropriate name/role/value. The audit said that keyboard users won't recognise the expanding accordion controls as tabs and are unlikely to intuitively use the arrow keys to navigate them. Each accordion control should be left in the tab order and the user should be able to press Space key or Enter key to open them. Focus should then move to the expanded content. This will make the controls more intuitive to people who are unable to see them. Could you address these issues?"

I was able to confirm this by testing our test content: https://h5p.org/accordion