iOS iPad - Deploy App - Enterprise Distribution

Our company has developed an App for iPad. We currently hold an Enterprise License with Apple. What we have been unable to do is DISTRIBUTE the App. Even after erase and rebuilding all certificates, provisioning profiles, etc, we get the same message while trying to Over-the-air distribute: "Unable to download application". Kind of like this error: [login to view URL] After many attempts we're checking if any freelancer with far more experience then us could do this small job.