DMU rejected my committee letter.

I tried to reply to the email explaining that the letter they rejected is in fact, my committee letter and should meet their requirements but their reply said that the committee letter I submitted is just a personal reference from someone and doesn't reflect the recommendation of an entire committee.
I'm trying to brainstorm as to why they are thinking this. Maybe the author of the letter forgot to write "on behalf of the committee" or maybe they didn't put it on a proper letter head??? I do know that the committee coordinator has gotten to know me really well over a year time period and basically knows my life story. Maybe her letter came off as really personal because of that? And if that were true, I would think that would be a strength and not a reason for rejection.

Now my school's committee is involved to hopefully resolve this misunderstanding. It's just frustrating because I had to go through a 6 month process to get that letter which included
15 essays, 3 workshops, a mock interview, a long application, meetings with the advisor.. etc. To have them flat-out reject just doesn't make any sense.