The Microsoft Managed Home Screen App requires overlay permissions in order to show the floating home button. Despite having permissions, it still requests it and no matter what you do, it just doesn't allow it.
No changes made to inTune and when this was previously logged, it suddenly started working.
Keen to see if anyone else has this issue and if they have been able to overcome it.
Quite confident that this is not an Android update as we have some older tablets (with older versions) that are experiencing the same issue.