Unable to share a notebook

Unable to share a notebook

I’ve been using your Notebook app for years and it’s my favorite. 
Recently I started working with a friend on a project and I want to share my notes with her.
She created an account and I made all the necessary steps to share the notebook with her, but there’s an error when I add her email address (it’s the same one she signed up with). The error message is in the screenshot I attached. I also tried sharing a link with her, but when she clicks on it the notebooks appears to be empty. Please help because we really want to use your app and not switch to a different one. I already made so many notes in this notebook.
Looking forward to your response!
Thank you in advance.

          Zoho Marketing Automation
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