Pull the motherboard fast ram out (all of it) and try again. Make sure you only use 2MB chip ram and memory on the accelerator.
Another thing you could try is remove the ram from the accelerator and leave the 4MB motherboard fast ram as-is, and see if it all works. There were some early CSMKII cards which had bad tolerance if fast ram was also installed on your A3000 or A4000 motherboard.
If the above advices don't work, then it must be due to bad jumper settings on your A3000 motherboard, or perhaps a loose scsi cable, daughter board not plugged in, or similar.