Starting in November 2017, you'll no longer be able to override your campaign bid strategies with ad group and keyword bid strategies. This change will help make it easier to manage your bid strategies. You can still set ad group targets for CPA and ROAS strategies, as well as ad group and keyword CPC bids, but all ad groups and keywords in a campaign must use the same bid strategy. It’s strongly recommended that you remove all existing ad group and keyword bid strategy overrides. To use a separate strategy for a specific ad group, you can move it into a new campaign.