Hi, not sure how to resolve your inability to see the HDD, but in case you haven’t seen it, here is an older short thread on using a hardware based RAID (which implies to not really use it, as BTRFS is essentially a SW RAID): BTRFS on Hardware RAID (LSI/Avago controller)
If you look on other forums about BTRFS discussions you will see similar sentiments, as BTRFS is not aware of an underlying HW RAID …