Section C-door code 1371

[pvwalla10]

I am not sure what I do next. I have the blank piece of paper that is supposed to have the door code for the door in Section C. I have not been able to get the code to show. I have even resorted to getting the code from cheats (1371) but that does not even open the door. Have I missed some step or what? I am stuck.

[WindexGlow]

In an attempt to reduce cheating (or speed runs) you have to do everything you're supposed to before a door unlocks.

For you, you have to

Spoiler below!

Use the blank piece of paper on that black-light