HTTP New Record to AppSheet API -- field value for a REF field??

[questionguy555]

Hello, I am trying to use HTTP Post/REST API to create a new row in an AppSheet child table (this is a google sheet). The child table has a column that is a REF type to the parent table (this is a different google sheet). The REF column in the child table is the ParentID value to relate the row to the parent table.

My HTTP Post action is attempting to upload the new row in the child table with the correct ParentID value (for an existing parent table row with matching ParentID value). However, Appsheet is rejecting/erroring on the HTTP Post/Add action:  

"detail": "REST API invoke request failed: Error: Can't add or update a row because of an invalid value. Update the value and try again.\n\n\tRow ID to correct: c30ff849 \n\tInvalid value for column ParentID: 12232de8",

EXA of the HTTP Post Action:

{

    "uri": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",

    "method": "POST",

    "headers": {

        "ApplicationAccessKey": "xxxxxxxxxxxxxxxxxxxx",

        "Content-Type": "application/json"

    },

    "body": {

        "Action": "Add",

        "Properties": {},

        "Rows": [

            {

                "ChildID": "c30ff849",

                "Date Added": "2025-05-05T10:07:28Z",

                "Note": "SCHEDULED - 05/06 at 10am -  She needs help with her pool light.\n",

                "User": "xxxxxxxxxxx",

                "Date Modified": "2025-05-05T14:07:29Z",

                "ParentID": "12232de8",

                "LastUpdatedBy": "xxxxxxxxx"

            }

        ]

    }

}