Thanks for your reply @steven-matison .
I was trying to use FlowFile Form Data Name in the InvokeHTTP processor

Someone gave me the right way to resolve my issue and it worked :
https://nifi.apache.org/docs/nifi-docs/components/org.apache.nifi/nifi-standard-nar/1.15.3/org.apach...
When the HTTP Method is POST, dynamic properties with the property name in the form of post:form:<NAME>, where the will be the form data name, will be used to fill out the multipart form parts.
so, post:form:<NAME> could be used for multipart/form-data
and you want application/x-www-form-urlencoded
format of http body should be parm1=Value1&parm2=Value2
before calling invokeHttp use replaceText with approximately this expression in replacement value:
client_secret=${client_secret:urlEncode()}&client_secret=${client_secret:urlEncode()}&...
then use invokehttp with
Send Message Body = true
Content-Type = application/x-www-form-urlencoded