NJ Unemployment appeals process?

So I was terminated from my job of 12 years for suspicion of theft. I was the branch manager here and I had 1 employee working under me. There was an account manager who worked at this branch who was using my user ID and password to log into our system. My employer claims that there were questionable transactions done under my user ID and this was grounds for termination. I applied for unemployment and was denied due to gross misconduct. This account manager who worked at the branch is still there and I now have an appeal into unemployment to receive benefits. Let me say this, I did not and have never stolen anything from my employer. My manager knew that this account manager was logging into the system but nothing was ever done. He was not my employee so I could not discipline him. His manager also knew of this for months but no one ever did anything. Now unemployment is saying that I was fired for gross misconduct but I am receiving cobra benefits and I thought if you were fired for gross misconduct you could not receive COBRA. Any advice on how to handle the appeal? I am 99% sure that this account manager was responsible for these transactions. Am i going to have to prove this to unempolyment? And if so how can I do that with no access to the employers emails or transaction receipts? Any advice would help. Thanks. Sorry for the novel of a question.