Typically need to hard reboot to recover missing GPU, soft reboot isn't enough ...
I changed driver and mining software at same time...
Need to investigate if it's hardware related or not.
Mining is lot's of fun

Thanks !
I have seen that happen with failing risers or dirty PCIE sockets.
Make sense, I just came back from my shed. I cleaned my Rig with compressed air but didn't clean GPU contact.
If it fail again, I will clean them with alcohol and Q-tips.