I have used this exact code in the past but for some reason in the pack im playing it doesn't work anymore I followed the instructions just like normal but when it asked to press c for chest and other commands it wouldn't work I even just tried skipping the step by just pushing enter and that didn't work either. heres the pastebin code: 6qmBBLpz

This Pastebin works instead: bfJuxUgn

Whoever made this script was not aware of the keys api and hardcoded their key values instead of using keys.c and keys.enter.
A somewhat recent update to LWJGL changed those value, the keys api was updated accordingly, but any script that uses hardcoded values will break because of it.

As Anavrins mentioned, there were several unavoidable changes in the 1.12 → 1.13 update, one of which changed the key codes. In most cases this shouldn't break programs - only when people hard coded constants.

It should be fairly easy to fix on your end - just replace them with the appropriate keys.$whatever values.