You’re attempting to duplicate an existing ad, and instead of creating a new ad from scratch, you want to leverage the engagement on that ad. But you can’t.
You get this message when trying to check the box to duplicate:
“This option is not available on new copies when the original ads were customized for different placements.”
If you customize the text or creative by A placement is a location where your ad is shown. Examples include Facebook's mobile Feed, Messenger, Instagram feed, Audience Network, right-hand column, and more. More in that ad, you won’t be able to duplicate it to leverage that engagement.
There’s a workaround, but it’s not perfect…
Edit the existing ad that you want to duplicate. Click the Share dropdown menu and select Facebook Post with Comments.
In the URL after POSTS, copy the string of numbers before the question mark.
This is the post ID.
Create a new ad. Within ad setup, select “Use existing post.”
Click the link to enter the post ID. Paste the ID we copied earlier.
This allows you to promote the existing Facebook post from the other ad. It won’t include the other placement versions, and if you customize by placement it will generate new posts from scratch.
Like I said, it’s not perfect. But this approach at least helps you leverage the engagement on the Facebook post, which was likely to generate the most engagement from the original ad.