Violation of Level 2 probation?

am on Level 2 Probation, and I recently got a Subpoena to appear in court for a Violation...... I have not had a dirty Urine Nor do I do drugs, I called my PO to let her know I wouldnt be able to make it in on the agreed date due to having started a new job. I asked for her to call me back so we could schedule another time for me to come in, and she never responded..... I then this past weekend got a Summons. What is the worst thing that can happen???? My charge was issuing a bad check, and I just started this new job so I should be able to start paying my restitution with out any problems......