Had to replace both drives, amber light now

That will be because the Duo’'s operating system is also on the drives. Did both drives fail at the same time? If you had replaced one then it would have worked, What Wd do is sell pre-configured drives for the Duo that have the Operating system on them.

The only other option is to perform a de-bricking procedure.

See: [GUIDE] Debrick a MyBookLive DUO