In the test configuration, you can specify to save http request when check failed. After running your test, you will know how your check failed.
Open your job, select the TaskGroup where your script will be executed. Select the VU configuration tab.
Save Request Details Check the "Save Request Details" to make Virtual Users log their HTTP traffic. These information will be available at the end of the job execution in the VU Details view.
After running your job, Virtual Users Details will appear. This indicates HTTP traffic has been logged by a VU.
Open the Checks View, check messages will appear as a Hyperlinks.
Click on it, the Virtual Users Details will be open with the request details selected where your check failed.
Clicking the Preview button will render the HTML in the HTTP response into a web page where it is easier to see why the check failed and what the response was from the server.