You need to have the Data page open at the time the packets are received. (And even then sometimes nothing is shown, while, e.g., an MQTT client does show the incoming data. I don’t know why.)
As you have the Data Storage integration enabled you might also see recent messages that were received while the page was not open. I think that goes back only a few hours, so that might explain why you don’t see those. (But even for very recent messages this too might not show anything at times; I don’t know why.) See also Why application data is shown as historical?