Exchange App for iOS and Android issue

I have exchange server 2007. I have 4 users right now (the number keeps growing) That are unable to get email to load from the Outlook app. However if I add their accounts to the built in mail app everything comes through just fine...

The Outlook app apears to log in and connect, and it shows up in the Mobile Device Manager in EMC. However nothing syncs. No email, no calendar, nothing.

The users prefer the Outlook app and would really like to get it working again.

I tried:

1. "Resetting the account"
2. Removing and Re-adding the account.
3. Updating the app. (Its running version 4.1.37 and doesn't see any updates in the play store.) (Its also worth noting I have lots of working users that are still using this version.)
4. Removing the devices from EMC>User>Manage Mobile Device (and then re-adding the account)

Any ideas for me?

Thanks,

Jared Jamiel