Nighthawk AC4000 3x3 tri band WiFi Router—going off and on with ATT fiber Giga, mainly Apple devices

[Jmvlg]

Hi, my router has 4 years and since some time already, the internet goes off and disappears from the WiFi list of available networks on Apple. I reset quite often the fiber, modem, router boxes. Problem remains. ATT has this security free service (firewall?!?!) turned ON, could it be the problem? Should I switch it OFF? I believe I had donde that too and no big difference on R8000P going OFF and ON, irresponsiveness. Thank you

[FURRYe38]

What Firmware version is currently loaded?
What is the Mfr and model# of the Internet Service Providers modem/ONT the NG router is connected too?
Be sure your using a good quality LAN cable between the modem and router. CAT6 is recommended. 

What channel configurations are currently set on the router?  Try 1 and 40.

Be sure to disable any MAC Address randomizers on phones and pads while at home:
https://community.netgear.com/t5/Nighthawk-App/NETGEAR-Mobile-Applications-and-Apple-Devices-FAQ/td-...

[Jmvlg]

Here:
- Mfr and model# of the Internet Service Providers: Arris, BGW210-700, SW ver. 4.26.11; AT&T Miami-Florida

- channel configurations currently set on the router?: 2.4GHz on 3, 5GHz on 48 -- I will change it and run a congestion detection for each band.

Thanks.

[FURRYe38]

Try channel 1 and 40. 

Also check the ISP modem. That's a gateway modem with built in router and wifi.  This would be a double NAT (two router) condition which isn't recommended. https://kb.netgear.com/30186/What-is-Double-NAT
https://kb.netgear.com/30187/How-to-fix-issues-with-Double-NAT
Couple of options,
1. Configure the modem for transparent bridge or modem only mode. Then use the Orbi router in router mode. You'll need to contact the ISP for help and information in regards to the modem being bridged correctly.
2. If you can't bridge the modem, disable ALL wifi radios on the modem, configure the modems DMZ/ExposedHost or IP Pass-Through for the IP address the Orbi router gets from the modem. Then you can use the Orbi router in Router mode.
3. Or disable all wifi radios on the modem and connect the Orbi router to the modem, configure AP mode on the Orbi router.
https://community.netgear.com/t5/Orbi-WIFI-6-AX-AND-Wi-Fi-6E-AXE/Procedure-for-Factory-reset-of-RBS8...
https://kb.netgear.com/31218/How-do-I-configure-my-Orbi-router-to-act-as-an-access-point and https://www.youtube.com/watch?v=H7LOcJ8GdDo&app=desktop
Try option #2 first...