I know this post is a little bit old, but I'll post the fix just for the records, it might be helpful for you and others.
This problem has been around since Google added a new privacy feature to their browser(I think it was last year 2013), and to be fair, it's good feature to keep your browsing more safely.
I've seen a lot of blogs complaining about it, and they didn't actually know what was the cause. They've gone far away with their thoughts on how to fix it, especially when Google haven't released any fix or mentioned how to fix it, while the fix won't take more than 5 seconds

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Long story short, here is how you fix it :
Go to Chrome browser settings
chrome://settings
then go to
Privacy
Then, from
Privacy, click on
Content settings button.
Now, on
Cookies options, untick "
Block third-party cookies and site data".
Then click
done, and go back to Youtube and refresh the page using
CTRL + F5 keys.
Now you should mark this thread as FIXED

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Regards,
iSR5