Got a denial letter for unemployment, what now? - 8 months and counting

My claim was denied after 17 weeks of waiting, and the letter says I have a short window to appeal. I have been trying to stay organised about it. My employer's version of events does not match mine, and I have emails that show it. If you have appealed before, what helped you prepare?

I printed my emails in order and wrote a one-page timeline. The hearing officer kept going back to it.