Error Querying Knowledge Base via API

Hi everyone, I'm new to VoiceFlow and was trying to query my knowledge base via the API, the query is successful from the API doc website (https://developer.voiceflow.com/reference/post_knowledge-base-query).

But when I copy the JSON body and send a test request with the API block, I get a "message : Invalid value" that I have attached here. Does anyone have any idea what I could be doing wrong?

And this is my JSON body
{
"question": "Test"
}