TestNav usually displays this error due to network connectivity problems. Follow the instructions in the error message. If given the option, you can choose a different customer.
Verify the network connection, and try again. If you cannot connect after the second attempt, close TestNav.
A network administrator may help you to resolve these issues by confirming the following:
After you restore the connection, check the student's test status in the administrative application and reset, if needed. Then, you can resume the student's testing session and have the student log in.