Why can't I use the "Optimize for 'X' conversions" bidding option with my Custom Event?

Selecting "Optimize for 'X' conversions" initiates conversion optimized bidding. This requires the following:

• A campaign using the "Conversions" objective
• An active Base Pixel
• An active Standard Event or Custom Event 

To use conversion optimized bidding for your campaign, check to ensure your Base Pixel is active. Custom Events will not function without an active Base Pixel.

Conversion optimized bidding for Custom Events also will not work if an ad set has less than 20 conversions. Just like with Standard Events, we only recommend using conversion optimized bidding after an ad set generates a minimum of 20 conversions per week. Having less than 20 conversions will result in little to no ad delivery.

Until an ad set receives 20 or more conversions, we recommend optimizing for clicks (CPC) or impressions (CPM).