Error Network When try to Connect to the server from the mobile app

[openou]

Hello,
We have deployed zammad in our internal servers so we want also to use this amazing mobile app but when we try to log in an error is occured and i don't know what we should to do exactly to perform the connection between the server and the mobile app

But we can log in using the browser from our phones and computers from the internal network and the outside

Error : Network Error