The current version of the Hoopla Digital app, 4.25, fails to function properly if reading an audiobook with VoiceOver enabled. I've reported the issue to developers and received a reply that they are aware of the issue and are working on a fix, but they don't have a schedule for release.
If you're unfamiliar with the app, Hoopla lets you check out audiobooks from your local library, then serves as an audiobook player for those books. However, in the current version, the playback controls are not accessible when VoiceOver is enabled.
If you're a Hoopla user, feel free to submit this issue yourself. Perhaps they'll fix the issue faster if more of us chime in. To submit feedback, select the About button in the top left corner, then select Submit Feedback. After submitting feedback, you'll get an automated email. Reply to that email, and they'll provide more information.