Google Chat Rest api which are used to create/update message is not working? getting 500 Internal server error?

I'm trying to post a message in Google chat through Chat rest api, but it's not working. Note : These api's were working fine before.But from yesterday it's not working. API : https://chat.googleapis.com/v1/spaces/{space-id}/messages

Request Body :

{
  "text":"Post Message reply",
  "cards":[
    {
      "header":{
        "title":"Card attached",
        "subtitle":"check for subtitle",
        "imageStyle":"AVATAR"
      },
      "sections":[
        {
          "widgets":[
            {
              "keyValue":{
                "topLabel":"toplabel calue",
                "content":"new content for my hangout bot",
                "contentMultiline":true,
                "bottomLabel":"bottomlabel string displyed"
              }
            }
          ]
        }
      ]
    }
  ]
}

Error Response:

{
  "error":{
    "code":500,
    "message":"Internal error encountered.",
    "status":"INTERNAL"
  }
}
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