Fortigate 60D UML 295 Configuration

Hello,

Does anyone have any experience configuring a Fortigate 60D using USB modem as redundant internet with basic failover?  The firmware version of our fortigate is v5.2.10,build742 and the USB modem model is a Pantech UML 295VW.

I've been able to get this working on an Fortigate 80E however not on a 60D.  When I enable the LTE-modem in configuration, the USB-WAN interface status is constantly on "initializing....".

Any help would be great!