Step1: Check firewall and antivirus is closed
Step2: Check the internet connection.
Step3: Close Google Chrome and go to the following path.
(C:\Program Files\Apache Software Foundation\Tomcat7.0\webapps\OES\exam Client\resources\Exam Client)
Step4: Right Click on the Exam client and Run as administrator.
Step5: Start the OES browser your issue will get solved.
In case of any query kindly raise the ticket for the same.