Some YouTube links won't open

Sometimes a YouTube link won't open in a message in Apple Mail. The YouTube window opens when the link is clicked, but after trying to start the movie, says: "an error occurred, please try again later". I checked the finder-window-activity pane as ordered, and there were 6 of about 20 items that said "forbidden" in red letters. It gave no instructions on how to fix them, however.

These same links open on our MacBook laptop and iPad with no problem! What gives?

I tried to post this earlier, and got no response after a week. I reformulated the question with more information.

Thanks