It sounds like the SCSI Controller on the GVP Card is enabled, Jumper JP4 is open, Close JP4 and the Card should boot properly.
In my experience GVP and CBM SCSI cards have never worked together, it's either one or the other. Another possibility is to connect the SCSI HDD to the GVP Card and remove the A2091 Controller. (They are both use RDB but the SCSI Device Name will need to changed from HDtoolbox.) Note: I've never tried to do this so others more familiar with GVP Controllers will have better information. (My Expertise was always Comspec SCSI Controllers)