MR60 — Nighthawk Mesh WiFi 6 Router

my mesh 60 system internet only works on the 5.0 and guest network but not the 2.4 ho do I fix that

What brand and model devices are you using on the 2.4Ghz radio network? 

Is Smart Connected enabled or disabled? 

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?  
What channels are you using? Auto? Try setting manual channel 1, 6 or 11 on 2.4Ghz and 40 to 48 channel on 5Ghz.
Any Wifi Neighbors near by? If so, how many?

Has a power off for 1 minute then back ON with the ISP modem and router been performed since last update?
Be sure to restart your network in this sequence:
Turn off and unplug modem.
Turn off router and computers.
Plug in and turn on modem. Wait 2 minutes for it to connect.
Turn on the router and wait 2 minutes for it to connect.
Turn on computers and rest of network.

Has a factory reset and setup from scratch been performed since last FW update? A complete pull of the power adapters for a period of time after the factory reset then walk thru the setup wizard and setup from scratch with a wired PC and web browser. https://kb.netgear.com/22697/How-do-I-install-my-NETGEAR-router-using-the-router-web-interface
Recommend setting the default DHCP IP address pool range to the following after applying and a factory reset: 192.168.#.100 to 192.168.#.200.
https://kb.netgear.com/24089/How-do-I-specify-the-pool-of-IP-addresses-assigned-by-my-Nighthawk-router