Why won’t my password work?

When my unit starts up, it asks to input my code. The code I registered doesn’t work. Is there a factory code? This only happened once I unplugged the main connector from the unit and plugged it back in. If the only option is to reset it, then how would I do that? I can’t find anything, anywhere on how to do it. No forum or page in the manual. Holding down the power and/or function button at the same time doesn’t do the trick. I am at a loss of any ideas.