This error occurs if the Office365 Admin has not given users the ability to allow 3rd party application access.

Here are a couple links to help resolve this issue:

An administrator needs to approve the WebDrive application to talk to Azure AD, which then allows going into app registrations in Azure AD, finding the WebDrive App, and pushing it out to more people by adding them to it.

The Admin can also go to this URL and authenticate in order to get this setup and running:<TenantID>/oauth2/authorize?client_id=<AppID>&response_type=code&redirect_uri=<ReplyURI>&prompt=admin_consent