I'm trying to update my cloudformation template but the update is failing by giving the error:
Updating Cloud Formation stack: cos-test
Failed to create stack: cos-test. Reason: Detailed Message: Template format error: unsupported structure. (Service: AmazonCloudFormation; Status Code: 400; Error Code: ValidationError; Request ID: 4aacc0d3-5e9a-11e8-8941-055edca13c3c)
Status Code: 400
Error Code: ValidationError

Also it's not showing in the console that the update failed.
Tried to update the stack through my local CLI it works alright. Also I tested for any validation error through my local CLI, but there was no  error.

I'm facing this issue only for the update stack and create stack works perfectly fine for my template.