Can not copy Ad, weird subcode [...]

Hi, I have a weird issue while trying to copy an ad. The Ad was running for a couple of days without any issues, and all of it mandatory sections filled out, everything has a green checkmark on it. When I try to copy it through the MetaApi (POST: /{ad_id}/copies} it returns an error that the ad is missing required field (which I can not find in the meta admin portal). The error is generic and does not show what is missing..
The response:
message: 'Invalid parameter', type: 'OAuthException', code: 100, error_subcode: 2446391, is_transient: false, error_user_title: 'Ad incomplete', error_user_msg: 'Your ad is missing one or more required fields. Make sure that each section of your ad is complete.'