Uploading junit4 automation results to Zephyr scale cloud (free version) failed

I installed Zephyr scale cloud (free version). The Jira project is ProjectA wth the key PROJ, and there is a test case test case7 with the key PROJ-T14. After the file zephyrscale_result.json was generated from JUnit4, the command below was issued, but the response was " {"errorCode":400,"message":"Couldn't find any mapped test cases","status":"Bad Request"}" 

curl -H "Authorization: Bearer token_value" -F "file=@zephyrscale_result.json;type=application/json" https://api.zephyrscale.smartbear.com/v2/automations/executions/custom?projectKey="PROJ"&autoCreateTestCases=true&autoCreateTestCases=true

zephyrscale_result.json content is as follows,

{
"version" : 1,
"executions" : [ {
"source" : "test_trial.SampleTest.testSample",
"result" : "Passed",
"testCase" : {
"key" : "PROJ-T14"
}
} ]
}

The image of test cases is uploaded with this email. Could anyone please shed some light on this issue?

Many thanks