If you are trying to attach OneDrive files in Outlook Desktop see this article instead: https://support.pinnacletechnology.solutions/en/support/solutions/articles/4000195136-attach-onedrive-file-in-outlook-desktop


To attach OneDrive files in Outlook on the Web do the following:

  1. Create a new email in Outlook on the Web
  2. Click the attachments icon
  3. Select "OneDrive"
  4. A new window will open up.
  5. In the left menu select "Files" and then select the file you want to attach.
  6. At the bottom you will see a button that says "Share link"
  7. Click the arrow next to that and select "Attach"
  8. If the person you are sending the file to is within your oganization you can select "Share link" instead