Use Class C of Seeeduino LoRaWAN

Hello everyone,
I’m trying to use the Class C of the Seeeduino LoRaWAN but i can’t get it to work.
I already tried using lora.setClassType(CLASS_C) but the Seeeduino doesn’t react to any downlinks if there isn’t a uplink right before (which comes from Class A).

Is anyone able to help me with that? I couldn’t find a former forum post or documentation which helped me…
(PS. Im using TTN, just in case thats relevant.)

Best Regards,