Iplanner

3 possibilities. No way to know exactly why it's not longer available though as this is a user to user forum, not Apple support directly, and Apple rarely published why Apps stop being available on the App Store.

1. The developer removed the app from the App Store.
2. The developer abandoned the app, and it has since been removed by Apple if it's no longer compatible with newer iOS versions.
3. Apple removed the App because it violated the terms of service of the App Store in some way.

I see an app called "Iplanner - Proveedor" in the U.S. app store. However, as the screen shots and the description are in Spanish, I can't tell you much more.

If that's not the app you're looking for and you can't find the one you want, it's possible that the developer has stopped supporting the app and has removed it from the App Store.