White Screen please help!!

So basically, I downloaded the PBE client and I got onto it, now I went onto the practice tool to just try it out, and boom White screen, so I just uninstall because this happened multiple times. I hen decide to play on my other account, my normal one and WHITE SCREEN. I've re downloaded 5 times, used ool like 18 times, doesn't work. I don't know what happened. I play on a Mac. Also, Ive looked at other threads and I always says to use the connection page, I've downloaded the tool, and nothing happens, I doesn't fix!!!

Please help!!!!