XR1000 preventing Samsung TV from accessing Internet

Hi, I am an IT professional. I replaced a cable provider's flaky WiFi router with the Netgear XR1000.  I set the SSIDs and WiFi passwords to be identical to the old WiFi credentials. All devices (including a TV) reconnected except for a Dell laptop. I had to disable AX in order for the laptop to see the WiFi. 

There are a total of 7 devices connected to 2.4GHz WiFi, 6 devices connected to 5GHz WiFi, and 2 devices connected via Ethernet. 

Two days later, a Samsung Smart TV model UN43NU6900BXZA stopped communicating. It reports that it was connected to the WiFi, but not to the internet. I tried disabling Armour and that made no difference. The TV will connect to the internet if it is joined to a 4G hot spot, so the TV's WiFi module is not defective. The TV and the XR1000 are at the latest available firmware. The TV does not see the 5G SSID so I assume this TV does not support it. 

Should I try connecting the TV to the guest network? Should I disable 20/40MHz coexistence? Should I turn on smart connect? Use a DHCP reservation? 

Any suggestions would be appreciated. It's disappointing to deal with this on a $350 router. Thank you.