Thank you alzhao. Very good point and I thought this was the case. On my home/main router NAT says disabled that’s what I meant. I have forwarded port 53 DNS on that router (put 53 in External and Internal Port boxes) with the local IP address of the Mango (192.168.1.21) on the Internal Host box but that’s not solving the issue. There is a box there for External Host and I’m not sure what to put in it… Could that be it?
I have also forwarded port 53 on the Mango itself on the Firewall page. Many thanks for all your suggestions