Items present in the Notes folder of a Personal Archive mailbox cannot be viewed using Outlook Web App (OWA).
Notes in primary mailbox are visible through OWA.
By default, the Notes folder in archive mailbox uses the By Conversation view. Notes items cannot be displayed in this view.
To work around this issue, disable the conversation view on the Notes folder of the Archive mailbox. Use the following steps:
Log in to an archive-enabled mailbox using OWA.
Click the Notes folder in the Archive mailbox.
Click the Arrange by drop down box and un-check Conversation.