Relevant Product: Exclaimer Cloud - Signatures for Office 365
At the time of setting up the Office 365 subscription in the setup wizard, when the Exclaimer Cloud IP addresses are added to the whitelist - a prompt is displayed that tells you to run the Enable-OrganizationCustomization command.
This issue occurs because, in most of the Microsoft datacentres, certain objects are consolidated to save space. And, when you use the Exchange Online PowerShell (or the Exchange Admin Center) to modify one of these objects for the first time, you get the prompt to run the Enable-OrganizationCustomization command.
Exclaimer Cloud will automatically run the necessary commands for you, however, it may take up to one hour to take effect.
After some time has passed, try re-running the setup wizard again.