As you all know we have been working hard to try and resolve the issues and have been in close contact with Parent Hub. Please see an update below which has come direct from them:
Yesterday we released an Android update that fixes the "Unsupported file" issue you were having when trying to open documents in the Parent Hub app.
If the app on your phone hasn't automatically updated yet, please tap on this link to download the update from the Play Store: https://play.google.com/store/apps/details?id=uk.co.parenthub.parenthub&hl=en_GB
Once you've installed the upgrade you should be able to open all document attachments without issue.
If you're still experiencing issues after the upgrade, please email firstname.lastname@example.org to let them know.
Thank you for your patience and understanding as we try to iron out the issues.