I commonly place youtube videos into my posts, for years, using Atahualpa but have not been able to do so lately, the video just does not show up in the published post.

In my troubleshooting I disabled all WordPress plugins and there was no change. Reinstalled WordPress and Atahualpa and there was no change. Went back to old posts that did have video that worked in the past and none of them were displaying any video (youtube or otherwise).

Finally, I switched to the default theme for this year (twenty fourteen) and all the videos reappeared. I reenabled all plugins and the videos still appeared. Switched back to Atahualpa and the all the videos disappeared, so it looks clear to me that there is something in Atahualpa that is not playing nice with WordPress 3.9.1

I embed videos into my post by pasting in the embed code, provided by youtube, into the HTML editor, such as:

<iframe width="560" height="315" src="//www.youtube.com/embed/mWPgnbRYNRM" frameborder="0" allowfullscreen></iframe>

Sometimes I just paste in the link to the youtube video right into the visual editor, as such:

[youtube=http://www.youtube.com/watch?v=JaNH56Vpg-A]

Neither method works right now.

You can see that the youtube video is missing on my post:

http://drbobtechblog.com/dual-carbon...um-much-safer/

I do not have any way to roll back to the previous version of Atahualpa because my backups just don't go that far back so I would appreciate a fix or a workaround, please. Thank you.

I don't see where a video should be, the page looks fine to me…
P.s. don't forget to disable caching when making changes to the site.

Looking at the site in FireBug the player is there it just has a height and width of 0 so you can't see it. If I change the height and width, the player shows.