{"status":"error","message":"Your request was accepted, however a post was not generated","error":"Invalid Custom payload: no supported fields","validation":[]}%

I am tring to use incoming webhook for spotinst however when i try to test my team channel via curl :

curl -H 'Content-Type: application/json' -d "{"text":"testing"}" my-incoming-webhook-url I get

{"status":"OK"}%

And also I get the testing in in my group but when we try the real message which is send by spotinst i get error for ex.

curl -X POST -H "Content-Type: application/json" -d '{

"subject": "spotinst:notification",

"message": "{"accountId":"act-account-id","resourceId":"smi-smi-id","organizationName":" organization.","trigger_policies":"[spot-Instance Launch Issues]","accountName":"account name","resourceName":"resourcename","title":"Stateful Resume Completed","message":"Stateful resume action completed successfully. Instance Id: instanceid. Instance Type : c5.4xlarge. Lifecycle: SPOT."}"

}' my-incoming-webhook-url

ERROR:

{"status":"error","message":"Your request was accepted, however a post was not generated","error":"Invalid Custom payload: no supported fields","validation":[]}%