Just that its not their problem & its down to the seller. I've heard back from them today & they're happy to get a new head from China but it will be at least a month.
What did Dreame say?
Contacted Dreame who, after asking for lots of purchase info & videos don't want to know. I've contacted the seller now & hopefully get a resolution.
Have a look at post 10 in this German thread for the details.... https://www.mi-forum.net/threads/reparaturanleitung-dreame-t20-hauptb%C3%BCrste-rolle-dreht-sich-nicht.11213/
Apparently they are going to send out replacements but it may take over a month to receive. Who knows if it'll work. Seems like a design fault as they rushed to make and send these out. Even their indiegogo customers are reporting the fault, and most of them still haven't received their machines! The carpet brush is a new item for them and they've never had one before on their other vacuums, so I'm sure the rest of the machine is decent, but for us in UK a carpet head is pretty crucial! Make sure you contact support through dream techs email and through their aliexpres store to make sure you get whatever fix they offer eventually!