I've connected the asus to ISP router via lan 3, internet access is good. I've set up a static IP on ps5 and put the Asus in the DMZ of isp router and open nat has now now achieved. Not sure why it wasn't working before but it's good now.

Which port in Https web access from wan did you choose? I'm having double nat issue with ee smart hub. Internet works but none of the nat types features are working