An advertiser enables target cost-per-acquisition (CPA) bidding and notices that conversions decrease. What might cause this?

An advertiser enables target cost-per-acquisition (CPA) bidding and notices that conversions decrease. What might cause this?

• The target CPA bid was higher than the recommended amount
• The target CPA bid was lower than the recommended amount
• The conversion tracking code snippet was not added to the site
• The cost-per-click (CPC) bid was lower than the recommended amount