If you created a new Roku account when you set up your cameras, you'll have to link the TV to that account if you want to view them on your TV. The only way link a TV to a different Roku account is to factory reset it. Note that if you have any subscriptions paid through "Roku Pay", they're tied to your Roku account. If you factory reset the TV and link it to a different account you'll no longer have access to those subscriptions and you'd want to cancel auto-renew on those subscriptions.
Can you still log into the Roku account at https://my.roku.com using the email address that's displayed under Settings->System->About on your TV? If so, I think you could have just changed the email address of the old account.
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