Ranked Flex issues. Please help

So me and a group of friends are trying to play 5-person flex queue. However every time me and one of the people have tried to play together (Both unplaced and haven't played a game since last season ending Silver 3 and 2 respectively) it gives us an error that our MMR is to different. However we both queued solo and got put on the same team. So I am confused here. Is there a bug with Flex or?
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