We recently completed upgrading all display CPM campaigns on the Google Display Network (GDN) to viewable CPM (vCPM) campaigns. As a result, setting the activeViewCpmEnabled field of ManualCpmBiddingScheme will no longer have any effect. This field will be removed in the next version of the AdWords API.
You can learn more about vCPM on our AdWords Help Center. As always, if you have any questions, comments, or concerns, please contact us via the forum or the Ads Developers Plus Page.
Thanet Praneenararat,
AdWords API Team