Appeal deadline questions after an unemployment denial (Salt Lake City)

I got a denial letter last week saying I left my job voluntarily, but I was let go as a retail manager. I am in Salt Lake City, in case local advice matters. My employer's version of events does not match mine, and I have emails that show it. Did you bring documents or only talk?

Stay calm and stick to facts. Mine lasted about thirty minutes and felt more like a conversation than a trial.