can not log on Zoho Notebook from my mobile phone

I can log on Zoho Notebook on my computer by using my Zoho email address, but I can not log on from my mobile by using my Zoho email address, it shows my Zoho account doesn't exist, why is that?

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Migrate your Notebook data to the new, mobile Notebook.
Zoho Notebook is transforming. The new version will include exciting new features and a completely new user experience. The initial version will be mobile based, available for Android and iOS. A new web version will be available after the initial mobile release. With the release of the new Notebook approaching, we're migrating most of your current data to the new version. Once the new version is released, there will be an additional window to migrate your data. We will not provide access to the