/conversations?fields=id,name,participants,messages{id,from,message,to,attachments{id,image_data,name,video_data,file_url},shares{id,name,link,description,template},created_time},updated_time&platform=instagram

When using this interface to obtain private message data of Instagram accounts bound to the Facebook public page through the Facebook public page ID, no data can be obtained and the interface does not report an error