YouTube videos will not play-error message

It seems to be a problem only with certain YouTubes that people send me by email

Oh. I was thinking that you were referring to the YouTube website. Apparently not?

• Receiving video files by email can sometimes be a problem, as the attachment size may be more that supported by your ISP, resulting in missing or incomplete files.
• Receiving video files in other formats than MP4/MOV/M4V may not work with QuickTime Player. You could try a different media player instead, e.g. VLC Media Player.

YouTube videos will not play

Why do you link YouTube to QuickTime Player? They are pretty much independent.

error message

What is the exact error message that you get?

Quicktime shows a change made on Jue 9, 2020 that I did not make.

Where do you see this date?

Do you have automatic updates on?

When I click on the Quicktime icon, I get a blank screen. Is this normal?

It is quite normal. Depending on your settings, QuickTime Player may launch with an Open dialog box that has an initial view for iCloud Drive. If you have no QuickTime content saved to iCloud previously, then that initial view will be blank.

To have QuickTime Player’s Open dialog box point to your Mac’s disk instead, change the folder location option in the sidebar of this Open dialog box to a location with QuickTime files on your Mac and open one. QuickTime Player should remember the last used view (folder).