The above error indicates the the exam's LockDown Browser settings could not be detected. For Canvas users, this may be due to you not letting each page fully load before clicking on the "Take Quiz" button.
The open tab in LockDown Browser contains a “spinner” indicator that tells you when the page is fully loaded. In the case of the below example, the spinner is indicating the page has not yet finished loading.
A closer look at the “spinner” indicator:
When the page is fully loaded, the spinner will disappear. You can now proceed.