I appreciate your answers, but unfortunately, they are both not solving this problem... If the banner is served on an ad network the same problem is occurring.
I have the kit settings to include both "localhost" and the IP 127.0.0.1, but the fonts are still not displaying... the last publish date was Sept. 25 at 8:46 p.m. eastern.
Any further help?
I'm sorry you ran into trouble here. Typekit font licensing does cover using web fonts in banners that will be placed on third party sites, but the implementation can be a little tricky as you noted.
If you know the domain name of the site(s) which be using the banner, you can simply include them on the kit and Typekit fonts should work as usual.
If the banner may be used on a variety of unknown domain names, however, the best option is to serve it in an iframe with a known src attribute and include that source URL on your font kit. The iframe referer will match the URL in the src, not the parent page, and the fonts will load within the iframe.
Another option is to use a font which is available in the Adobe Edge Web Fonts collection:
Edge Web Fonts are free, so there is no referrer checking required; they will work on any domain name. And the Edge Web Fonts are served from our font network, so you get the same speed and reliability as you do with Typekit. Edge Web Fonts does not include the full Typekit font library, but there are many similar selections which may work for your advertisement.
I hope that this helps; let me know if you have any other questions.