Skype for Business on premise installation wont allow mobile devices to sign in

We have recently installed Skype for Business to completely replace our ageing PABX. We have 2 X Sonus SBA's and 2 Pool servers.
We have all of our certificates in place and the Microsoft Remote Connectivity Analyser comes back with no errors.

We get this error when signing in on a mobile device:
We cant sign you in. Please check your account info and try again.


If I turn logging on with the Skype for Business App on the iPhone it says:

2015-11-01 23:29:56.285 SfB[2213:19fbc7000] INFO UI SFBAlertMapper.mm/35:Mapping error code = 0x2203000f, context = handleUcwaAppSessionRequestError, type = 300
2015-11-01 23:29:56.286 SfB[2213:19fbc7000] INFO UI SFBAlertMapper.mm/1859:Mapped error message is 'We can’t sign you in. Please check your account info and try again. 
2015-11-01 23:29:56.347 SfB[2213:19fbc7000] INFO UI CMSettingsManager.mm/233:CMFirstViewController SETTINGS_LYNCFIRSTRUN_APPLICATION 1
2015-11-01 23:29:56.382 SfB[2213:19fbc7000] INFO UI SFBTelemetryTracingProvider.mm/20: Telemetry Service record visit to view: CMCredentialsTable
2015-11-02 07:29:57.527 SfB[2213:748723] [HTTPSTACK] Network read (2048): 
2015-11-02 07:29:57.528 SfB[2213:748723] [HTTPSTACK] Response: 200
2015-11-02 07:29:57.529 SfB[2213:748723] [HTTPSTACK] Request dtor this=0x13722aa10, m_Session=<__NSURLSessionLocal: 0x135de8680>, on Thread <NSThread: 0x135d927d0>{number = 11, name = (null)}
2015-11-02 07:29:57.530 SfB[2213:748723] [HTTPSTACK] Request dtor this=0x13722aa10, on Thread <NSThread: 0x135d927d0>{number = 11, name = (null)}
2015-11-02 07:29:57.530 SfB[2213:748723] [HTTPSTACK] Request dtor this=0x13722aa10, Session 'https://pipe.skype.com/Collector/3.0/' invalidated
2015-11-01 23:29:58.474 SfB[2213:19fbc7000] INFO UI SFBTelemetryTracingProvider.mm/10: Telemetry Service: ShowAdvancedOptionsTapped
2015-11-01 23:30:01.327 SfB[2213:19fbc7000] INFO APPLICATION CUcwaDataSynchronizer.cpp/1015:Mode 1 scheduled to timeout in 120sec
2015-11-01 23:30:01.424 SfB[2213:19fbc7000] INFO UI CMTableViewControllerBase.mm/286:MEMORY TRACKING 0x3722a080 CREATED CMLoggingViewController
2015-11-01 23:30:01.998 SfB[2213:19fbc7000] INFO UI SFBTelemetryTracingProvider.mm/20: Telemetry Service record visit to view: CMLogging
2015-11-02 07:30:02.317 SfB[2213:747012]  is not a valid email address.

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We can login to Skype within the domain environment on a PC with no problem.
We can also login to Skype outside the domain environment on a PC or Mac running Skype for Business / Lync 2011

We can't sign in on iPhone, Lumia or Android using the SFB App.

Any help would be greatly appreciated.