Hi Kilaru,
Thank you for reaching support. I would recommend to check the specific service, say ResponsiveDisplayAdInfo or GmailAdInfo for the dimensions of image supported while uploading the image via API. If you are still facing the issue, please share the complete request and response logs along with the client customer Id for me to investigate further? Please use Reply privately to author option while sharing the details.
Regards,
Nikisha Patel, Google Ads API Team