I use Google Chrome and have no trouble getting the free ball.
The biggest issue seems to be that people don't understand where the ball is given. On the second screen, where you go to play a game, a pop up appears, once a day only, and gives you the chance to watch a 30 second video. After watching it you click on continue and the ball is put into your bag. There is a tournament going on as well, that lets you attempt to hit a shot close to the hole and enter a competetion for prizes. This is also run by Dove but doesn't get you the free balls.
There is a limit of one ball a day and I believe that after you get the one, the free ball advertisement goes away until the next day. Thanks to Dove for giving the balls to the WGT members, hopefully more sponsors will do this, I think it is a win / win for all the parties involved.