Why won’t my password work?

Try a general Google search for "jvc 650 reset" or "jvc 650 password" to see if there are any pages or posts about the default factory password or hard resetting the security feature. Worst case scenario, the deck will need to be sent in to JVC for factory reset - JVC required this for some model as a security feature to prevent stolen head units from functioning. You can give JVC service a call, but it might be difficult to reach someone who actually knows what to do. I'd try shooting them an email first - be specific and be prepared to follow up.