I added the smart app banner meta tag to my page and it was working fine at one point yesterday. However, now the banner only appears as a gray bar with no content in it. It appears to try to load something for a second, but then stops. Not sure what I changed in the code that would break it. Link for screenshot included below or see for yourself live:
I think the service is currently down.
Been having the same problem myself, have just tested the ted.com site and theirs doesn't load either.
Hope that helps!