Downlink to device not working

Issue: Uplink works, Downlink does not work

Setup: RAK7258 and Arduino Leonardo with Dragino LoRa Shield v1.4

LoRa® Server: Built-in Server

Details: The device does send data successfully to the Server and the Server publishes the data via external MQTT server. If I try to send downlink data to the device either via publishing to the applications …/tx MQTT topic or via the Application → Edit Device → Downlink page in the RAK web UI then nothing is received on the device.

I use the sample code from arduino-lmic/ttn-abp.ino at master · matthijskooijman/arduino-lmic · GitHub on the device currently which should print the number of bytes received as downlink if data is received.