Not much really. You can afford to fail the NPPE exam quite a few times without any consequence, except that you need to pay the corresponding fees each time, and depending on the association, wait for some time before taking it again, especially after the third attempt.

The system works as follows: to be eligible to take the NPPE exam, you first need to file a formal application for licensure to the association of the province or territory where you intend to practice a as professional engineer or geoscientist. The association then communicates your eligibility to take the exam and the time window within which you can take it. During that time window, you are allowed to take the exam up to four (4) times. If the window closes or you failed the fourth time, then your application for licensure is withdrawn and you need to re-apply for licensure and the system repeats itself.

So, how many times can you take the NPPE exam? Literally, as many times as you need to pass it, except that you need to pay the corresponding fees each time, and depending on the association, wait for some time before taking it again, especially after the third attempt. You may also need to file a new application for licensure after the fourth attempt.