Powershell rest api update custom field

Hi

I am battling to get to grips with the rest api.

I am using the below PowerShell script which does not throw any exceptions

can anybody shed some light on my dilemma

The full story:  { I am using powershell to identify status changes in Web help Desk database, and create issues in JIRA for my KANBAN board ( Via the rest api) the response from Jira is the issue number Just created,

I now want to update Web Help Desk "ticket custom field"   with this JIRA ticket Number.}

any help appreciated

Thanks

$definitionId="33"

$restValue="E1245"

$uri=http://10.5.67.159/helpdesk/WebObjects/Helpdesk.woa/ra/Tickets/36566/?username=Andren&password=zzzzzz

$body= @{

  definitionId=$definitionId

  restValue=$restValue

   $jsonBody=ConvertTo-Json$body

   $resp=  Invoke-RestMethod-uri$uri-MethodPut-body$jsonBody-ContentType"application/json" 

     $cat=$resp.id

    write-host" key = $resp.id"

------------------------

after execution returns The Id of the ticket as expected, but no update happens

I get the info I deem necessary from this command line in chrome, I also use to inspect if my update has worked

http://103.52.67.159/helpdesk/WebObjects/Helpdesk.woa/ra/Tickets/36566/?username=Andren&password=xxxxxx

which returns details of the ticket to viewing pane  Ticket id = 36566

{"id":36566,"type":"Ticket","bccAddresses":null,"ccAddressesForTech":null,"departmentId":null,"lastUpdated":"2014-11.................":"TicketCustomField","definitionId":31,"restValue":"23333"},{"id":15947,"type":"TicketCustomField","definitionId":32,"restValue":"Accounting / Financials"},{"id":18080,"type":"TicketCustomField","definitionId":33,"restValue":"233332"},{"id":