We think our HOA board member is in collusion with contractor

Recently a Building committee chairman (also a board member) that I suspected of collusion with a contractor, 2 other committee members and property manager, was asked 2 questions by registered mail. He did sign for the letter, but 35 days later, I have no response....what is the law in Florida. I was under the impression a registered letter was to have some type of response within 30 days. Please help...