It would usually mean there4 was a violation of some condition of probation. When a violation occurs, you may be sentenced to any jail time previously stayed. The court may elect, however, to determine there was no violation or it may find a violation and reinstate you on probation without additional jail time.
If you were reinstated on probation, that would indicate there was an alleged violation of probation. It means that the court found you were in violation of probation but instead of executing your sentence you were reinstated on probation subject to conditions of probation.