OK, sounds like Dr PBX is correct, the lines were not punched down on the correct ports.
Are there ANY telephone system technicians in the area?
Proposal, contact a Mitel Tech on the board, get a commitment and a $ quote. Then contact a local tech who will be willing to be the on-site hands and eyes, so to speak. Then borrow the console, get everybody together and get it fixed. But first, try to find a Mitel tech in your area.