Last night I tried tethered shooting in EOS Utility with my 5D Mark III using studio lights and a sync cord. The strobes would not fire when using Live View. They worked fine through tethered shooting with out Live View.
So, I did some digging and found that under the Live View settings you have to set Silent Shooting to Disabled in order for the body to trigger the strobes. Why? No flipping idea.
Anyway, thought the info might help someone, so I've shared.
I realize this might be common knowledge already, but I had no idea.