If you go up to the throne room and pop through the coloured portals there, it will show you the sequence for that colour with the two missing symbols that you've to use to unlock the final portal.
Is that what you need to know?
They're saying that the portals near the gnome throne haven't opened up, so they can't get to the incomplete version of the code.
You don't mention this, so it seems like the most appropriate question to ask first:
Have you defeated the guardians following each trial? The portals near the throne don't appear until after you've defeated the relevant guardian.
