You may find that not everyone you expect to see the posts published by your application will be able to see those posts.
Firstly, ensure that you have set the default privacy / visibility of the application to the desired level (described in step #20 of the application creation section on this help page).
Secondly, you might have missed Steps 19 and 20 of the Facebook application creation instructions.
Thirdly, the reason could be because your Facebook application is still new. Facebook has complex algorithms that surface interesting posts for a user and that combat spam. We will not be surprised if new applications are treated with suspicion by those algorithms and that the audience (or visibility) of the posts published by the application is intially very limited regardless of your default settings. We speculate that it would be almost like a "trial period" for an application to determine if it will be a good citizen of Facebook.
If this is the case, then only the passage of time and consistent high quality posts that are not reported and are liked or commented on by others should allow Facebook's algorithms to increasingly widen the visibility of the posts published by the application. Unfortunately there is no way to short-circuit this process and there is no "work-around".
Can't find the answer to your question? Create a support ticket for personalized support by our staff.