The error
ASPECT_RATIO_NOT_ALLOWED is usually experienced when the aspect ratio of the image is not allowed in AdWords. That said, before creating an ad in AdWords, you will have to prepare an image file that is sized and formatted appropriately. You can refer to
this article on how to upload images for the allowable size and dimensions. For
Responsive display ads, you can refer to the dimension and size specifications listed
here.
Let me know if you have any other questions.
Bharani, AdWords API Team.