I'm folding for some 30 years and I can't remember beeing stuck at step 6 ... until now
the diagrams are confussing: up to step 4 valley and mountain folds are shown correct, then at 5 valley folds are used to show, where the hiden corner will be after "unhiding" it; starting with step 6 all of a sudden dotted lines are used for valley folds; the diagram at 7 is wrong (there is no triangle on top, in my model there are no creases that are shown there).
I suggest as follows:
) fold step 1
) fold step 2
) only open sink the top as shown in 3
) mountain fold as shown in 4
) the "hidden corners" mentioned at 5 are not hidden now: closed sink them (they will be placed afterwards as indicated with the "valley folds" in 5)... now they will be hidden behind a white flap you should have
) valley fold this white flap up
) valley fold the other flap up (the one that was "hidden"
) repeat on the other side
) valley fold and unfold dividing the angle as shown in 6
) repeat on the other side
) now you can use the creases to get step 8 (as I said: the diagram in 7 is wrong)
step 9/10: you can fold the flap up, diving the angle, folding a rabbit ear, unfolding once again and you have all creases shown at 10 ... as I mentioned: dotted lines are used to show valley folds ...
) I didn't manage step 11 and 30/31 ...
hope that helps