Your Competitive Rank is currently around 700-800 Bronze. Unfortunately, that range accounts for a fraction of 1% of the entire player pool. One of the current rules of Competitive Play is to try and pair up groups of the equal number together as much as possible, or pair a group against smaller grouped opponents of higher SR. In extreme cases the matchmaker can even cancel your search queue if it cannot find a fair pairing for you. As such this is not a bug or a technical malfunction.
Personally, I feel for your situation and I am very happy to see that you and your friends are grouping up to try and work together as a team. I am not a fan of “Group Priority Matchmaking” and even have an entire topic written about it in the Competitive Discussion forum. I still recommend trying to group up despite this disadvantage. Cheers.