Should I be trying a different selection instead like TAPE or DVD or just hitting the power button?

The Tape and DVD are just labels. On the new to you 500 you can test one of those or label a new unlabeled button on the Main screen. I think we've determined that the menu & #3 buttons on your old remote don't work since they didn't work for your TV and Sunfire so coding a new Main button there still won't get you the Menu & #3 working. The label has nothing to do as to which codes to use. You can label the button anything you want within 5 characters.