Hello kevinyo12, try to remove the youtube cookies, see how to do that : Delete cookies to remove the information websites have stored on your computer and check it again, if the above does not solve the issue try to delete the cookies.sqlite file and any cookies.sqlite-journal files in profile folder(in case cookies are corrupted), see : Remove corrupt cookies file

thank you

Hi ideato, thanks for taking time to answer my problem. I've done what you suggested. It still doesn't work. Thanks.

Reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

• Press and hold Shift and left-click the Reload button.
• Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• Press "Command + Shift + R" (MAC)

Clear the cache and the cookies from sites that cause problems.

"Clear the Cache":

• Tools > Options > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

• Tools > Options > Privacy > Cookies: "Show Cookies"

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do not click the Reset button on the Safe mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Hi cor-el. Thanks for your suggestion. I started firefox in safe mode and it seems that one of my extensions (AdBlock Plus) was causing the problem.

You're welcome and thanks for reporting your findings.