Duplicate the problem:
Open a web browser, such as Chrome and enter the developer tool by selecting the F12 function key.
Select Network tab and check "Preserve Log".
Navigate to Youtube.com
Search for site exhibiting the behavior. Example: Search for “Solo” and attempt to play a video.
View the Developer (F12) log listing 403 Errors.
Note the 403 errors would also be visible if you run a forensic report in the WSS portal.threatpulse.com
Check one of the URLs with the 403 error not going through WSS. Example: Use a host using a browser (Firefox): https://r2---sn-qxo7rn7e.googl
If you receive a 404, examine the certificate details by navigating to Extensions> Certificate Subject Alt Name. Check the list and verify categorization: sitereview.bluecoat.com. Example: drive.google.com is categorized as storage, it will block these requests if they are blocked by your policy.
Note: WSS looks at the certificate subject alt names (SANs) and will evaluate them.
Web Security Service