LoRaWan nodes primarily transmit, and rarely receive anything.
First you need to check and make sure that the node transmission was received. Being too close to the gateway is known to cause mixups.
Additionally, there’s very little evidence that there presently exists any software which can make a bare-radio pi-based node actually work correctly. Few node applications would be compatible with using a pi, so it’s not really a configuration that gets much work from people able to debug such a thing and get it to work correctly.
The switchover to TTN v3 makes correct handling of downlinks absolutely mandatory for all nodes - as a result, it’s likely the death of various “not quite complete” node softwares.