MR1100ATT HotSpot/Router IMEI 015161000328446

So I guess this MR1100 is a Modem Hotspot/ Router the thing is it works Great by its self but when tring to connect to another Netgear product it wont most of the time??? I have this Mr1100NightHawk M1 Mobile Router and my sisiter has the same device. We noticed that if I connect My MR1100 (With The Teather option under Setup To Enable)it Work Great and Increases the Signal by About 1 to 2 Megabits per sec. The Device that I am Connecting to My MR1100 is the NetGearNightHawk AC1900 Smart Wifi Router Model R7000 With a cat 5E patch cable(A regular lan network cable). The problem is my Sister has the Exact same MR1100 Modem/Router that I have but for some reason it must have different Software installed because hers doesnt have the "Teather" option under the setup tab for the MR1100??? I have done the Check for updated software online thru the Routerlogin.net after logging into the ATT site to manage the MR1100 it says Software is up to Date Current Ver Installed, but the Problem is I goto Netgear under the Downloads and there is a Newer version of Firmware Available that the Mr1100 Wont install??? I downloaded the Firmware but cant find anyway to get it to install??? I tried the NightHawk App for Mobile phones and access the MR1100 thru the app and I get the Same results most current Ver Installed??? is there a way to force the MR1100 To install Firmware even when the Device says that it has the most current ver of Firmware installed??? I'm just Guessing that the Reason my Sisters MR1100 doesnt have the "Teathering" option under the Setup tab for the Mr1100 Router is Because of the Firmware installed I might be wrong but I'm sure thats what it is? If anyone know why My MR1100 has the "Teathering" option and My Sisters doesn't Please let me know :-) as she wants to connect the MR1100 to another Router(The Nighthawk AC1900) to increase the Signal in her house. My MR1100 Works Great connected to the Netgear Nighthawk AC1900 Smart Wifi Router, But only when the "Teathering" option is Enabled under setup.....Her MR1100 Doesn't have this option??? 

If you know what the problem is Please let me know what I need to do to get my Sisters MR1100 working with another Router??? I don't care about the Brand name of Router and have Tried Cisco Routers also and same Problem it will not pass the Signal thru any router connected to it thru a LAN Cable??

Thanks in Advance Scottie D.