Cannot Resolve Gateway Down and Local ACL Denial errors

Hi. Please excuse my lack of Firewall / Networking expertise in advance.

I have configured my Home Sophos XG in Gateway Mode (Running DHCP Server with the same Subnet Mask as my Cable Modem/Router), connected my Cable Modem/Router via the WAN Port and my "other" Wireless Router (no DHCP) via the LAN Port.

However I have 2 related issues;

1. I cannot resolve "Gateway Down" status and
2. I cannot reach the internet from my "other" Wireless Router

Thinking this was Firewall Rule related, I created an Any, Any, Any rule to test, to no avail.
What am I missing or how do I diagnose my error(s), as all I see in the Security Policy Log Viewer is Local ACL Denied for both Ports.

Please help !

Peter