This error occurs when you have the LockDown Browser installed for another institution (most likely your university) besides mbaprepworks.  The easiest solution to this issue is to uninstall the LockDown Browser from your computer, restart, download and install the LockDown Browser from the link we provide on the final exam page (a version tagged to our institution) and then click the, "Launch LockDown Browser" button to launch the LockDown Browser and start the exam.