Floating IP the same on HA pair?

Failover should occur in the order defined under device-management / traffic-groups / traffic-group- / Failover Order.

Note that the device-group must be in sync for this to work - if you've just changed the order, and not performed a sync (and auto-sync is not enabled), then the next active device shown on the traffic-group will not necessarily reflect the order specified in the failover order.

If the order is configured so that the current device is not allowed, a failover will not be triggered - you will need to do that manually by forcing the active device to standby (or offline, which is a bit overkill)