Can’t Downlink to device from API to Chirpstack

I have problem about control lamp by LoRaWAN using Chripstack,I testing LoRaWAN for control Lamp (device), I create API for connect to chirpstack then test downlink to Lamp Device by unit and group it work lamp can switch open – close or dimming change, but this time I can’t control lamp by downlink in group multicast anymore , in chirpstack can detect and show the data but lamp don’t have response ,I check the connection is ok, can anyone help me for solve this problem?

[quote=“NOPPON_RUNGKUHA, post:1, topic:16063”]
I check the connection is ok[/quote]

Are you 100% sure the modem is getting the downlink? For example the modem I work with, I hook it up to a serial port and I can see the downlinks, that way I can make sure, you have something like this or how do you know?