When you open a codelist in Code Manager and want to create a .GCT file make sure that the codes you want active have a checkmark on it. I'd also recommend keeping a .txt file backup of your codelist so you can edit it at anytime. Another thing I sometimes forget is when I add a new code to click the "save modifications" button before creating the .GCT file or the awesome new code you added won't be there.
Lol. Nobody even gets the joke :D