What exactly did you do?
Did you assign persistent INTERNAL IP ADDRESS to whichever device you wanna use as SERVER?
If you don't specify correct port and internal IP address, there is no way for the router to decide where to send the incoming connection and leads to drop of the connection.
There is a guide on the forum. I am currently busy,would link it when i have time. You can try searching the forum. @GeekBench
How do you think NAT table would work if it does not know which INTERNAL IP address is the target of incoming connection?
NAT 1 and NAT 2 are useless configuration unless your NAT table know how it should handle incoming connections....
You need to specify a port formward entry in the ONT so that it know that theincoming connection are to be directed to which downstream device.😉