Downlink not detected

we are testing downlink on a wireless shell, though uplink works fine and we receive messages correctly, any attempt to send a downlink is not detected by the device. we see confirmed and unconfirned messages managed by the chirpstack server and transmitted by gateway, however no messages detected by device.
we are using mode C

How do you send the downlinks?
What server do you use?

My first guess is that you may be using the wrong fport?
If you can monitor your gateway, check if the message is scheduled and sentd.

Add some more detail to your question, please.

we are using mikrotik gateway with chirpstack 4.01 anf fport 1 both uplink and downlink. frequencies Eu868
everything works fine in uplink, problem is just downlink not detected by wireless shell.