I think this may be a Mountlist problem. The PowerFlyer will automatically detect hard drives, but ATAPI devices should have a Mountlist located in Devs/DOSdrivers.
For the Rewriter, you can use the CD0 mountlist, which comes with OS3.1 (in the Storage drawer). Copy this into Devs/DOSdrivers.
Also make sure that the CD0 icon contains the correct Unit Number for the CDrewriter device. Check in Workbench's Icon/Information menu. Type in and save the correct setting.
Also the device driver (where required) should always be device=scsi.device
If you have only one HD on the Primary Channel, this is Unit 0. If there is only the Master CDrewriter on Channel 2, this is Unit 1. If you have any Slave units on either channel, adjust the Unit number accordingly. That is:
Channel1 Master Unit 0
Channel1 Slave Unit 1
Channel2 Master Unit 2
Channel 2 Slave Unit 3
Cheers,
JaX