This time around I set a requirement in the Build Journal section that requires all new threads to use the "RRBBO13" prefix. You need to select that prefix next to the title of your build before it will let you post.
Here you can see the prefix menu display when you mouse over the (No prefix) notation...
Here's what it looks like when you did it right...
Here you can see the prefix menu display when you mouse over the (No prefix) notation...
Here's what it looks like when you did it right...