Great question — answering as the UphillTech team:
I have not seen any additional press release, so this is likely your issue . Twilio had issues at the carrier level and blocked groupmms for all new customers. So if you have an older account (or access to one) you can potentially use it, but otherwise as of their last statement you can't use it at the moment still. The work around I've seen is to use conversations and distributed it a message via a one to many channel, but I have not tried this myself and I'm not familiar with the drawback. Also there are limitations on the phone numbers as well.
Full answer by Lucas Hendren: https://stackoverflow.stackexchange.com/a/76751408 (CC BY-SA 4.0).
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