Each machine walkthrough eliminates your ability to earn points on that machine. This means if you view a machine walkthrough before you have fully exploited it, you will be unable to gain points from this machine. If you have submitted all the flags before viewing the walkthrough of that machine, your points will not be deducted.
A machine walkthrough is automatically enabled after a machine is started. There is no limitation on viewing walkthroughs for fully exploited machines. For machines you haven't fully exploited, you are only able to access one machine walkthrough in a 24 hour period.This is by design, as we encourage you to first try yourself - the ideal way to bolster a Try Harder mindset.
For information on accessing walkthroughs, please visit this Help Center article.