Safari showing black screen for YouTube

Hello,

I have a MacBook Pro (13-inch, Early 2011) running OS X 10.10.3 and Safari 8.0.5.

About a week ago, I tried playing a YouTube video on Safari, but was met with only a black screen. I reloaded the page several times, quit then reopened Safari, and then removed AdBlocker, but the video didn't play. I then tried playing the video on Google Chrome and it worked, so I know that the issue is related to Safari. I've looked at several other threads and have done the following to no avail:

• Cleared Safari cookies for YouTube (Safari --> Preferences --> Privacy --> Details)
• Install ClicktoFlash, but that didn't work, so I uninstalled it
• Uninstalled Flash and reinstalled (latest version of Flash Player installed)

Can someone please help me out and tell me what I can do to get YouTube videos to play on Safari?

Thanks!