Devices Connected to Internet but say "No Internet"

[CodySF57]

Model: RAX10 (For some reason can't select that one in the list)

Firmware: v1.0.3.92 (shows as current on the Nighthawk App and website last I checked)

I got this router a few days ago and set it up.  Setup went fine and for the first day it worked swimmingly. Sometime around the third day I'm looking at my phone and it says "No Internet" while connected to the network I made from the router, but everything seeemed to work. This message is annoying since my phone will often reconnect to my modem Wi-Fi and my connection seems to randomly drop when I have an ethernet connected to the router.

I've tried rebooting the router through the app and physically, but the error persists.

I've seen some fixes by changing the IP address from static to dynamic but I'm not seeing that option.

Any help is appreciated thank you.

[plemans · Accepted solution]

which is a modem/router combo device. 

It can cause a double nat. 

https://kb.netgear.com/30186/What-is-Double-NAT

How to fix issues with Double NAT | Answer | NETGEAR Support

[plemans]

what modem/gateway is it connected to?

[CodySF57]

BGW210 from AT&T.

I

[plemans · Accepted solution]

which is a modem/router combo device. 

It can cause a double nat. 

https://kb.netgear.com/30186/What-is-Double-NAT

How to fix issues with Double NAT | Answer | NETGEAR Support

[CodySF57]

Ah thank you, didn't even think about that. I'll work with my ISP to setup the bridge mode on my modem.

[CodySF57]

Went ahead and changed my Modem/Router into bridge mode and logged into the router using the web address opposed to the Nighthawk app. 

Everything is working on my router and it is showing online.

Thank you.