Facebook App not showing in a page but showing in another, why?

I've created a facebook application and a test fan page. I added the app to the fan page (Test page) and it immediately created a tab in that page. But when I added the same app to another page it didn't create a tab. Does anyone know why? I the app tab name is set correctly and does not conflict with any other tabs. Both pages have basic facebook apps added to them and nothing else.

Am I missing somet开发者_运维技巧hing?

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Looks like I forgot to set the Tab Url field in the app settings. Once I fixed it, removed the application and re-added it. It worked fine