What do you mean by "failing"? A peep fails at their job if they start, then a small cloud appears, they step away shaking their head, and say "Uh-uh". In that case, if you drag them back to the computer they should start again. Eventually, when they start to gain skills, the failure rate will decline.
However, if they arrive at the computer and simply shake their head, it is likely that another family member has "booked" the computer and is on their way to use it, if they're not already sitting there. You can usually override the booking system by dragging your peep to the computer, or by interrupting the other peep, then dragging your first peep to it.
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To err is human; to arr is pirate.