I need help a very simple app attached run using the API interactive documentation tool that's built into Alteryx Server.
I'm running version 2021.1.4.26400
I've been successful running apis numbered 1 and 2 below but stuck on 3

The app I'm trying to run is attached.
I've tried different apps from different machines and always get the same bad 500 return
I am running in chrome on the server logged in as the main service account and have the app in the main service accounts private studio
The questions I'm providing in 3 are
{
"questions": [
{
"name": "Input String",
"value": "abcd"
}
],
"priority": ""
}
Response detail is:
Request URL
Response Body
{
"data": null,
"exceptionName": "UnknownException",
"innerExceptionMessage": "",
"message": "Unknown error.\nArgumentException\nRequestID: 190a389a96914e83a8b3dcf475566a0c"
}Response Code
Response Headers
{
"Access-Control-Allow-Headers": "Content-Type, Accept, Authorization",
"Access-Control-Allow-Methods": "GET, POST, PUT, DELETE, OPTIONS",
"Access-Control-Allow-Origin": "*",
"Access-Control-Max-Age": "1728000",
"Content-Type": "application/json",
"Date": "Thu, 16 Jun 2022 13:30:19 GMT",
"Transfer-Encoding": "chunked"
}