Dell Gateway 5000 with Ubuntu Core 16 sim card issue

Hi,

I am using Dell Gateway 5000 with ubuntu core 16 on it. I want to make the gateway as access point and use the sim card to connect to internet. I am inserting the sim card in the card slot, but gateway is not identifying the sim card. The mobile network LED stays off when I power the Gateway after inserting sim card. It is as if the sim card is not present at all. 

Can anyone help me understand what could be wrong here?