On Jenkins Integration with Jira I see below error. I have Junit in Post build actions

On Jenkins Integration with Jira I see below error. I have Junit in Post build actions.
Total Test Cases : 1ERROR: Build step failed with exception
org.json.JSONException: A JSONObject text must begin with ‘{’ at 0 [character 1 line 1]
at org.json.JSONTokener.syntaxError(JSONTokener.java:503)
at org.json.JSONObject.(JSONObject.java:213)
at org.json.JSONObject.(JSONObject.java:430)
at com.thed.zephyr.jenkins.utils.rest.TestCaseUtil.assignTests(TestCaseUtil.java:315)
at com.thed.zephyr.jenkins.utils.rest.TestCaseUtil.processTestCaseDetails(TestCaseUtil.java:641)
at com.thed.zephyr.jenkins.reporter.ZfjReporter.perform(ZfjReporter.java:101)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:818)
at hudson.model.AbstractBuild$AbstractBuildExecution.performAllBuildSteps(AbstractBuild.java:767)
at hudson.model.Build$BuildExecution.post2(Build.java:179)
at hudson.model.AbstractBuild$AbstractBuildExecution.post(AbstractBuild.java:711)
at hudson.model.Run.execute(Run.java:1917)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:44)
at hudson.model.ResourceController.execute(ResourceController.java:101)
at hudson.model.Executor.run(Executor.java:442)
Build step ‘Publish test result to Zephyr for JIRA’ marked build as failure
Unable to figure out what is the exact cause of issue, can anyone help.