- Make sure you have only one router with DHCP enabled; to handle IP assignment across the network.
- The router that has DHCP enabled should have its IP address changed to a none default IP Address; just incase one of the other routers get reset to default causing an IP and DHCP conflict. (Ex: 10.10.2.1 or 192.168.2.1)
The below posts will give you the clues you need:
https://community.linksys.com/t5/Wireless-Routers/Cannot-access-router-2/td-p/709605