motorhaven - 5:55 pm on Jul 2, 2013 (gmt 0)
As noted I also tried from a different different IP - not even close to the other range, from a completely different PC. After posting, I called a friend up (different state) and asked him to browse. Couldn't see it either, verified it was in the HTML. Other pages not using that ad slot displayed ads okay.
But here's the kicker, about 10 minutes after this problem... the ads started showing up again in this slot. I couldn't resist trying again, changed ALL ad slots to ASYNC and they work.
A side note: like Google DFP you only need one of these even if you have more than one slot on the page:
<script async src="http://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
So my experience is it worked, but temporarily seemed to hiccup the first ad slot I tried it on. Pretty busy site with a good advertiser and I've never seen it display blanks until this, thankfully just for a few minutes.