Could anyone tell me why wont DJI GO 4 app be compatible with the apple mini 2?

Just to verify, you mean iPad mini 2, right? It supposes to be compatible with Apple iPad mini 2, could you tell me more detail about the incompatible so I can help you with?

Yes its the iPad mini 2 when i hit download on the store i get "app not compatible" or something like this

Could you please provide a screenshot of the error message? Normally, the iPad mini 1 will get a warning which states the iPad is not compatible with the APP, not the iPad mini 2.

Here is the screenshot   http://imgur.com/a/pNAk9