I decided! I scratch my head for hours, and of course I find the answer 30 seconds after posting on StackOverflow!
It seems that the guest account is not a member of all users, so assigning the Project Viewer role to all users is not enough.
You must explicitly assign the Project Viewers role to the guest user. This is vaguely done on a completely separate screen in the User Guest Settings section, associated with the upper right side of the primary user screen. Walla! Completion of the assignment.
Tim long
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