RH236: Guided Exercise: Extending Tiered Volumes

Hi all

Anyone else stuck on this? I've tried this a few times now but each time the "gluster volume tier prod-vol detach commit" appears to work but "gluster volume tier prod-vol attach" fails (as does "gluster volume tier prod-vol detach status") with "Volume tier detach status: failed: Volume prod-vol is not a distribute volume or contains only 1 brick." Neither of which are true. Its a replica with two bricks.

Any ideas?