If you also subscribe to NOW with one of their TV Memberships, then you could always factory reset the NOW Box and set it up from scratch again.
If you are only using the NOW Box for third party Apps such has Disney Plus etc and don't want to subscribe to NOW or have a current NOW active subscription, then don't factory reset the box (otherwise to get the box running again you will have to start a 7 day NOW Hayu trial or start a NOW streaming TV Membership).
Like @gavs82008 said the previous owner should have really factory reset the box before getting rid off it to remove all trace of their account details on any Apps or NOW service they have used on the box.
Hi @SCOTTHANNAM ,
The previous owner should have really wiped their information off the box to avoid things like this happening and for other security reasons when moving the box on to somebody else.
If it's a NOW branded box, then from the NOW main home screen, keep clicking on the back button (button next to Home key) on the NOW remote until you see a hidden extra menu on the left hand side of the TV screen.
Then select My Apps, then highlight the Disney Plus App, then there should be an option to remove the App by pressing the star button on the NOW remote.
Then go to Apps Store on the LHS menu, then add the Disney Plus App again.
This should give you a fresh App for you to use your own Disney Plus account login details.
After that, maybe go into Settings on the LHS menu and update the software on the NOW box.
Do a factory reset to clear everything from the box, this does mean you’ll need to log back in to apps again. However if the user who gave away the box did that then you wouldn’t be in this mess.