can not ping netgear nighthawk m1 mr1100

Dear Nighthtawk M1 friends,

Our devices are able to connect to the internet via the LTE router after putting T-mobile sim card (hotspot plan is required). In the local area network (LAN), these connected devices can ping each other.

But we can not ping it using external computers. Port forwarding and DMZ are both set. However, we just can not ping the public ip asscociated to the LTE router.

Maybe we miss some setup to open the permission of the router. Hope to hear your expertise.

-- Luke