CRM For Mobile Not Working

Hey Everyone,

I have an instance of CRM 2015 On-Premise that I'm trying to connect to with mobile applications. I've configured and setup IFD and also did the additional steps for Mobile and Tablets as defined here:

https://technet.microsoft.com/en-us/library/dn889580.aspx

I can reach the CRM system from outside network with the https://orgname.domainname.com, but when I try and set up Mobile (both on Android and Windows phones) as well as on tablets (the Windows 8 CRM app). After typing in the URL I can 'sometimes' type in credentials, but I seem to get hit with errors like:

'Your server is not available or does not support this application'

Any thoughts? Thanks