Hello,
I used to use a CV64-3D with P96 on my A2000.
Once in a while, when I booted up my Amiga, the RTG screen stayed black.
After many trials, I found it was the monitor driver I had chosen during the P96 installation. The horizontal frequency was a bit too high and from time to time the monitor didn't manage to sync on the RTG display. I choosed a lower frequency driver, and everything went well. I don't know if it could be this thing in your case, but you cuold check to make sure your frequency settings comply with your monitor.
