Well, I got in and actually won! I think I figured it out. Watch which door leeds to the prize on the round before you play. Count, what order it is picked up. Then watch the order placement of the doors while the are being set up.
For example...
There are seven doors set out. Door 3 wins the round before you play. After the prize is awarded, the winning door is picked up third. Watch very carefully where the third doors is set once the set-up begins for your round. That should, in theory, be the winning door... That is how I won...