CustomObject 'Order' Page layouts from orgs created from orgs prior to V39 may have in the layout metadata <excludebuttons>Activate</excludeButtons>

For V39 (and possibly earlier) orgs, 'Activate' is no longer the OOTB API name for the button with label 'Activate'. The button API name is ActivateOrder. Hence, deployment fails with error "In field: excludeButtons, no such standard action:Activate"

There is no workaround except to exclude the Order layout from the Gearset Selected Objects. This is not a good workaround for a commonly-used OOTB SFDC Standard object.