I recently moved into a new house, that has FIOS, but had FIOS at my previous house as well and are having the same issues I had the old house. I'm using a ASUS ZenWiFi router as an access point to extend the WiFi coverage beyond the basement where the FIOS router is connected. I'm having issues where devices, like my desktop or laptop stop resolving IPs. I have the ZenWiFi hardwired as an access point with the SSID as the FIOS router. They are connected intially but eventually they loose internet access and nslookup fails to resolve basis sites like espn.com. At the old house I swapped out a couple of different access points and still had the same problems. Does FIOS not support bringing your own personal Access Point to extend coverage?
Did you follow REF https://www.dslreports.com/faq/11233
In my own words that FAQ.
#1 In the primary NAT router:
a) find the DHCP Range.
b) Make sure that it does not occupy the whole subnet.
c) If it occupy the whole subnet, make it smaller.
For example with it at 192.168.1.1 with the subnet mask of 255.255.255.0, the first DHCP Address that it handles out is 192.168.1.2 and the last DHCP Address that it handles out is 192.168.1.254 - then you could change it so that the first DHCP Address that it handles out is 192.168.1.100 and the last DHCP Address that it handles out is 192.168.1.254
#2 For that other router, you must:
a) Have it disconnected at this step.
b) Set it's LAN IP Address with the same Subnet as the primary but outside of the DHCP Range of the Primary router's DHCP Range.
For example with the primary IP Address 192.168.1.1 with the subnet mask of 255.255.255.0, the first DHCP Address that it handles out is 192.168.1.100 and the last DHCP Address that it handles out is 192.168.1.254 - then the other router's LAN IP Address could be 192.168.1.6
c) Disable the DHCP Server in the second RJ-45 WAN port NAT router.
#3 Once you make those changes, now you can connect both of those routers together but this time LAN to LAN.