Hmmm...I know I have an external SCSI CD-ROM drive working on my Amiga with Trumpcard 500. There is a 105MB hard drive inside the chassis.
Things to suggest (worth a try):
- turn on the Amiga with a CD-R in the tray instead of empty.
- change the order of the SCSI devices
- Have you checked that the LUNs (Logical Unit Numbers) don't conflict? This actually shouldn't be a problem if the devices are set to different SCSI device numbers. I'm not even sure you CAN change the LUN on a CD-ROM drive.
- try a different CD drive if you have one
I vaguely recall that this card was reported to be problematic with some removable media drives (that were made after the invention of the card).