Cannot access Raspi 4 with VNC viewer

[hushcoden]

I have a 4x port device (1x WAN and 3x LANs): LAN1 (192.168.0.1/24) is used as the main internal network and it's connected to a WAP.

The issue I have is that the when the Raspi 4 is connected to LAN1 to one of the WAP ports, I can use VNC viewer from my Windows laptop with no problems, but if I connect the Raspi 4 directly to the free LAN port on the device/firewall, I cannot - LAN3 = 192.168.20.1/24

I can ping the Raspi 4 from my laptop also when connected to LAN3, and in firewall -> rules -> LAN3 I have the 'default allow LAN3 to any rule' but VNC viewer goes in time out: can someone please help me out to troubleshoot?

Tia.