Multicast on The Things Stack Sandbox or Cloud?

Hi everyone,
I am trying to conduct a LoRaWAN multicast setup on TTS Sandbox v3. But I got the error “No downlink path available” even though I already specified the gateway ID in the json file through MQTT. I am wondering whether the reason is that multicast is not supported on TTS Sandbox? I also heard that the multicast is only possible on TTS Cloud/Enterprise. Does anyone get successful when configuring muticast on TTS Cloud/Enterprise?
Thanks.

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