These are discretionary, but let's imagine.... It could be anything that reflects the conditions. There are the optional conditions, but there are also what we call standard conditions, such as keeping the peace and being on good behaviour. Essentially the person did not comply with the condition, and the probation officers decided to take action against that individual.
It could be, for example, that he did not attend counselling as he was supposed to. He missed an appointment. Maybe it was just one; it could have been a series of them. It's difficult to say, but at some point a discretionary decision was made that the person wilfully chose not to comply with the condition. Then a warrant is issued for his arrest, usually, and he is returned to custody.