MR1100 Nighthawk LTE hot spot no internet connection to fire tv

Firstly I like to make it clear that I have no experience with Fire TV so this answer may be no help to you, but here goes...

Do you thing the problem could be that the Fire TV device isn't being allocated an IP address by the M1's DHCP? I've had similar problems from time to time: my M1 is connected via its Ethernet port to an unmanaged Gigabit Ethernet switch into which I have 2 dual-band WiFi access points connected to distribute WiFi around the house. I've also got a wired Ethernet connection from the switch to a desktop machine and a printer. For some reason, probably lack of Ethernet activity, the M1 Ethernet port goes to sleep and I lose connectivity all round. This can be woken by tapping the Power button on the M1 - after around 20 seconds connectivity is restored. But I've then had problems with the access points not having connectivity even after waking the M1. I'm guessing this could be IP address related. When this happens, the only way to get things running again is to shut down the M1 completely and start up again. It then reassigns IP addresses. Frustratingly, the printer gets a different IP address assigned so I have to check in the M1 web interface to see what it's assigned and then change the printer port details on the PC in order to print to it.

One way to check if this is the problem in your case would be to disable the M1 dynamic DHCP addressing and assign static IP addresses manually. This is of course not very convenient for mobile devices but would allow you to rule out this possibility.

Unfortunately, it's not currently possible to combine DHCP addressing with some manually assigned static addresses, as many router interfaces allow. If this were possible, it would solve my printer issue. I did request this relatively simple firmware modification in an earlier post but got no response from Netgear staff. I hope they read it...