That’s not how class C works.
It is not about receiving during RX2, rather it is about having the radio receiving with the air settings of RX2, all of the time except when it needs to be transmitting or briefly listening for something else (like RX1, etc).
Also it is not clear that your gateway is actually transmitting any class C downlinks…
when I go to the Live Device Data in the device page, I can see the packets I sent from the server as Ack.
What is that supposed to mean?