Update Datasources REST API operation for live connections

I am trying to update the connection string of a live connection power bi report published to the service. In order to do so, I am using the "Update Datasources In Group" datasets operation of the REST API.  I'm getting an "InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-RestMethod], WebException" in the response. Is is possible to change connection strings of published Power BI reports in live connection mode? Below is  what I am trying to do and the response that I am getting... Thanks,

Request

$body = @" 
{ 
  "updateDetails":[ 
    { 
      "connectionDetails": 
      { 
        "server": "$($targetServer)", 
        "database": "$($targetDatabase)" 
      }, 
      "datasourceSelector": 
      { 
        "datasourceType": "$($datasourceType)", 
        "connectionDetails": 
        { 
          "server": "$($originalServer)", 
          "database": "$($originalDatabase)" 
        } 
      } 
    } 
  ] 
} 
"@

$uri = "https://api.powerbi.com/v1.0/$groupsPath/datasets/$datasetID/Default.UpdateDatasources"
Invoke-RestMethod -Uri $uri -Headers $authHeader -Method POST -Body $body

Response

Invoke-RestMethod : The remote server returned an error: (400) Bad Request.
At H:\Projects\User Story 7483 - Infrastructure-Automated deployment of Power BI reports\20181003 Attempt\Change MOR Financial Report - Prod Orig to QA - Rest API.ps1:105 char:1
+ Invoke-RestMethod -Uri $uri -Headers $authHeader -Method POST -Body $ ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-RestMethod], WebException
+ FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeRestMethodCommand