When activating the Securlet for O365 it shows an error "failed to get authorization token from Sharepoint".
The Global Administrator user does not have a Sharepoint license. This could be because Sharepoint entitlement is not included in the O365 tenant.
Go to the Office 365 Admin console -> Users -> Active users. Click on the Global Administrator name that is being used to activate the Securlet. Go to the "Licenses and apps" tab for that user. Expand the Apps section, and verify that Sharepoint is checked.