Question

I deleted everything and reinstalled... but previous Licensing still appears

Answer 1

You should be able to go to your https://my.presonus.com and click on 'Register a Product.

When you have done this, Start up your Studio One. In Studio one click on the menu: Studio One and go to 'Studio One Activation'

You should get a popup asking for the key, Click that 'down' arrow on the right of that field and 'Show my existing product keys'

From here you should be able to choose between your registered keys and activate the one you wish to use