Unable to delete cover photo from Page through Graph API

Question

I can update the cover photo successfully through Graph API, by posting a photo, linking the photo_id with the cover photo and deleting the posted photo.

But I cannot delete the cover photo.

I tried 3 ways : Setting cover to empty through API

{
"error": {
"message": "(#100) Parameter cover: Invalid id:  ",
"type": "OAuthException",
"code": 100,
"fbtrace_id":
}
}

Setting cover to null through API

{
"error": {
"message": "(#100) Parameter cover: Invalid id: null",
"type": "OAuthException",
"code": 100,
"fbtrace_id":
}
}

deleting cover_photo_id through API

{
"error": {
"message": "(#200) App can only delete photos created by the same app",
"type": "OAuthException",
"code": 200,
"fbtrace_id":
}
}

Knowing that the same app was used to create the image post and to set the cover_id