Thanks for reaching out to us on HP Support Forums. 🙂 I came across your post and would like to help.
I understand that you have an HP Envy 17t series laptop. I read that the online videos always buffer. You have run the network check and it passed. I read that the internet speed is good.
To provide an accurate resolution, I need a few more details:
When was the last time the online videos played fine?
Did any software changes take place after which this issue may have started?
Are you able to surf the internet webpages with good speed?
Meanwhile, I did some research and suggest you to perform the following steps to fix this issue:
If the issue started recently then please perform a Microsoft System Restore to rollback the laptop to an earlier date when everything worked fine. This will not delete your data. Refer to steps mentioned under "Restoring Windows 7 to a previous point."
Post a successful system restore, you may try to play online videos and check.
If the issue persists then try opening the Youtube websites and other online videos in another browser like Google Chrome, Microsoft Edge, Internet Explorer, etc. and check the performance.
I hope this does the trick. Please feel free to keep me posted. Cheers! 🙂