@arborist
Sounds like you may have unlinked Roku devices. (2 seperate Roku accounts using different email addresses). You can go to Settings/System/About on the Roku devices and see if the email addresses (Roku accounts) match.
Then go to your online account at https://www.roku.com/, and navigate to My Account, then PIN Preference. See if there is a PIN requirement under the Adding of Channels, or Parental Controls for the Roku Channel. (make sure to do this under the account for the guest TV).
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Assuming for the above that the Roku is popping up a box asking for a PIN, not a password.
Perhaps you can post a screenshot of the message box and what channels/app the guest is trying to watch if still having issues.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
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