The formula
无咎, wú jiù: 无 is an old form of 無, "there is no," and 咎 is a fault, a mistake or a harm someone could hold against you. In Cambios we say "no fault." It's one of the formulas that recur most often in the book.
What it means
The Great Commentary explains it: "no fault" means you knew how to make good a mistake. It isn't the absence of trouble; it's having acted so there's nothing to reproach you for.
That's why it so often follows a warning. In the third line of Activity: "The noble person strives and strives all day long, and at nightfall is still watchful. Danger. No fault." There's risk, but attention covers it.
It isn't good fortune
On the scale of good fortune and misfortune, "no fault" sits in the middle: it doesn't promise a good outcome, it only says there's no blame. It's the mark of someone who did the right thing even when things were hard. Sometimes it comes as 无大咎, "no great fault": there was a small slip, nothing serious.
In a reading
If you get "no fault," you can carry on calmly, without expecting applause. If it follows a danger, notice what's protecting you: it's nearly always an attitude, such as caution, humility or honesty. Compare it with regret and distress.