। ॥ १६ ॥
In plain words
It is experience itself — so it never becomes something experienced. Grant that. Even so, not once, not a single time, can the doubt arise that it might not be. Its very existence is awareness.
Close to the Sanskrit
Because it is itself experience, although of this there is no being-an-object-of-experience, still not even once could the doubt of non-existence arise regarding that existence whose very nature is awareness.