I am getting response as {"error":"API not found."} for executing testcase

/public/rest/api/1.0/execution/c0f1a12d-d066-49d1-96c8-04a2c4e1d4b7
please help

String payload_runexecID="{\n" +
" \"projectId\":"+projectID+",\n" +
" \"issueId\":"+issueId+",\n" +
" \"cycleId\":\""+cycleID+"\",\n" +
" \"versionId\":-1,\n" +
" \"assigneeType\":\"currentUser\"\n" +
"}";