I also had problematic experiences with Mediator on an A1200.
From my experience the cards need to be sitted 90 degrees to the
Mediator busboard. If you put them a little angled towards the side it will moslty sure not be recognized. Even if it shows up in the PCI Info utility it doesn´t mean it´ll work.
Could you please copy the PCI Info output for the Voodoo card here?
Also, i had lots of troubles one time, and couldn´t get the Mediator to work for more than 10 minutes also, as said here already. Then i found that the Mach chips were suffering from oxidation. Try to remove them, one at a time, clean their legs with a pencil eraser, then remove the residual eraser with alchohol, and clean also the sockets. Then fit the chip and move for the next one. After i did this, i never had any more problems with my Mediator, untill the next clean up (once a year). As you said your Amiga was a bit messy, i think you have the same problem.
And by the way, never had problems with boards order, at least not after the 2.5 driver. But is recommended that the Voodoo be in the first slot (the topmost one).
Good Luck!
