WTFast not working on Windows 8.1

Alright, I got WTFast ( https://www.wtfast.com/ ), because I was like watching Brofresco ( https://www.youtube.com/user/BroFresco ) and I saw WTFast. So I tried it out on a game. Apparently, after champion select and onto the loading screen, there was a blank dark screen. So I alt + tab'd out of there. I exited out of lol and no, I'm not sure if I got the Fire Wall thing. Afterwards, I closed WTFast and rejoined the game. Later on, I found out that we were losing and I tried to catch up. We lost in the end. Anyone know how to fix this?