If in the Youtube website, the spinning thing in the middle of the clip screen will just keep spinning, and no video appears.
If an embedded Youtube clip eg as shown in UdonMap, the clip screen will just show "This video no longer available"
Very frustrating
I have now discovered an apparent solution to the problem (on Thai Visa).
If in the Youtube website, you may see an option just under the clip screen which says "watch in high quality". Just click on this and wait.
If the option is not there, simply add "&fmt=18" (without the "s) at the end of the web address at the top of your browser.
This will not work if you are trying to view an embedded clip. In this case simply left click on the menu button at the bottom of the clip screen. Copy (ctrl - c) the url address, then paste (ctrl - v) it into the the Youtube website, and follow the earlier instructions.
Good luck




