I found this post on google and seen is recent
I have a similar problem with 3dmark 99
the demo software for voodoo find my voodoo 2 without problem and run the demo perfectly
just running 3dmark 99 , the software can't find my voodoo 2 only my ati rage pro II+ pci

My setup
pentium mmx 166 mhz
64 mb of ram edo
video card : ati rage pro II+
voodoo 2 unknow brand 12 mb
usb pci card
dlink dfe 530tx
sound blaster 16
Windows 98se

also using or not irq adress , a voodoo 2 can be detceted by windows and not recognized by software , it happen to my when I rebuild this old computer past a month , i used the first pci due to cable position on the board and the video card on the second pci and it not worked properly , I tryed two card
Swaping the video and the voodoo fix this issue

Edit issue found
forget to update directx X , updating with the last update (june 2006) fix the problem