This message will appear when User Consent Permissions have not been configured to allow a user to give consent for applications to access their mailbox. To resolve this, an Administrator needs to configure user consent settings in Outlook.
Granting Folderly permissions
1. Sign into your Office365 administrator account.
2. Click Settings > Org Settings.
3. Select the Services tab and find User consent to apps in the list.
4. In User consent to apps, ensure checkbox is ticked.
5. Click Save.