AppSheet API error

[Will_Henry]

I am using a webhook action to hit the appsheet api to add rows to an app.

I have defined the body as follows:
{
“Action”: “Add”,

“Rows”: [
{
“Unique_User_Table_ID”: <<[Shift Manager Name]>>
},
]
}

But I am getting this error, saying the body is missing:

Error:
“Webhook HTTP post request failed with exception {“Message”:“REST API invoke request failed: The HTTP Body which should contain the API Action, Properties, and Row data is missing.”} The remote server returned an error: (400) Bad Request.”
Properties:
{
“AppTemplateName”: “GMToolkit-929004”,
“AppId”: “8885bb91-850f-4252-b256-7b32d88ddc59”,
“AppTemplateVersion”: “1.000081”,
“RuleName”: “SOR Passing Score Adds To Training”,
“EventType”: “Change”,
“InvokedBy”: “Add”,
“Server”: “prodv2-lb-1”,
“TableName”: “Evaluations”,
“RuleTableName”: “Evaluations”,
“OperationUpdateMode”: “ADDS_ONLY”,
“EventMatch”: “Workflow event successfully matched”,
“Condition”: “=[Score] > 0”,
“MatchesCondition”: “True”,
“ActionResults”: “Created 1 ActionResults”,
“Action Name”: “Add Entry To Training Tracking”,
“Url”: “https://api.appsheet.com/api/v2/apps/bfbcfeb8-188b-4231-9226-50982c30bb61/tables/TrainingTracking/Ac...”,
“Verb”: “Post”,
“MimeType”: “application/json”,
“Headers”: “redacted”,
“Payload”: “{“Action”: “Add”,“Rows”: [{“Unique_User_Table_ID”: Will J Henry_beaulaurier_4453}]}”,
“Operation”: “Change workflow rule”,
“Performance”: “{“Version”:1,“Time”:“00:00:00”,“PerformanceTimingRoot”:{“Mid”:1,“Params”:{“ParamList”:[{“Pid”:13,“Value”:“Evaluations”}]},“Timer”:{“Time”:“00:00:00”},“Children”:},“IsEmpty”:false}”,
“Result”: “Failure”
}

Any Ideas?