XF 2.2 My old BB code for embedding youtube videos no longer works

[Zardoz43]

Just in the last couple weeks my old BB Code imported from vBulletin to embed a youtube video in a post no longer works.

Did xenforo software change recentlly - did YouTube change the format of their video links recently?

Also it seems that just embedding the youtube video link directly in the post no longer seems to work
for example

https://www.youtube.com/watch?v=aU5OB2WopbU

used to embed a clickable video in a post. (testing)

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works just fine on this forum but not on my forum..... . CHECKING SAME VIDEO link ON MY FORUM

Yes, the raw, natural link does not work (any more) on my forum....
my Xenforo software translates it as if it were BB Code... to

[MEDIA]undefined[/MEDIA]

Can anybody suggest anything in the Admin Control Panel that might have accidentally changed???
My Xenforo software is up-to-date.
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And that [YOUTUBE] custom BB code was the only custom BB Code that was imported from vBulletin a year ago.