Connectivity issues between FVS318Gv2 & Nighthawk RAX75 WIFI routers (2)

Greetings.

Disclaimer: I am not IT savy like you all but do have some knowledge to handle simple settings.

I have continues connectivity issues with my Nighthawk RAX75 WIFI routers (2) which are connected via Cat6 cables to a Netgear FVS318Gv2 Firewall/router/switch which is connected via a Cat6 cable to a Spectrum Hitron Technologies E31N2V1 router.

The FVS318Gv2 has an IP of 10.23.23.10 and the RAX75 WIFI routers have an IP of 192.168.1.1 & 192.168.10.10 and are each DHCP enabled.

I have called Netgear Tech support and Spectrum to no avail.

The firmware of the FVS318Gv2 is 4.3.3-6. The router refuses to accept the latest supported firmware of 4.3.5-3-.

I understand Netgear no longer supports the FVS318Gv2 Firewall/router/switch. I am seeking help in troubleshooting the connectivity issues.

I also would like to know if it would be easier to replace the FVS318Gv2 with a new switch and if so what model should I replace it with. I would prefer 8 connection ports but could do with 6.

Any help and suggestions would be greatly appreciated.

Respectfully,

Yves