Maybe the "Video forum" here at CZ knows something about this.
The old embed code starts with....
the GREATER THAN sign (<) and the word "OBJECT"
The newer embed code starts with...
the Greater than sign and the word "iframe"
...(here in the post, I can't print these symbols followed by the words because the "greater than" sign is a computer code and messes with either the server or editor software).
If I remember correctly, I have gotten both the new code and the old code to work here at CZ (I prefer the old code so that I'm sure the code is always compatible with everyone's computer). Maybe your computer settings are wrong (don't know what it could be, just guessing).
When you go to the youtube video you want to embed, click on "SHARE", it will show the URL highlighted in blue below the videoscreen. Look below the highlighted URL and you will see choices,...click on "USE OLD EMBED CODE".