If I remember correctly, some models of the A2000 (the German Rev 4.3 comes to mind) need to have the 68000 CPU on the mobo removed for the 680x0 to work properly. Check the front left corner inside the case to see which revision you have.
Be very careful removing the 68000, as the pins bend easily, and most IC extractors don't handle 64-pin DIPs (I use a right-angled automotive "pick").
If this isn't the problem, then have a look at the jumpers. GVP is notorious for having jumpers that don't do anything but render the card inoperable - one may have been misidentified as a legit jumper, and set to the wrong position.
banzai
