Hi Latha,
Usually this error occurs if your CA Test Data Manager Portal service is not running.
Here is how to start the service:
1. Go to 'services.msc'.
2. Right click on the 'CA Test Data Manager Portal' service.
3. Click 'Start' or 'Restart'.
4. Re-launch the TDM Portal.
5. Re-test your scenario.
If you are still experiencing the issue, please open a support case so that we can further troubleshoot.
Best regards,
Taylor