A failed start on you interlock is most likely considered a technical violation. Probation officers generally have some discretion on which technical violations to report to the judge. What your PO decides to do will depend on how you've handled the other requirements of your probation. In my jurisdiction a person is not formally violated until the third interlock failure. However, you have two strikes in one. Not only did the interlock fail, but now there is evidence of alcohol consumption which is also a violation. Before your next visit, I would complete every condition of probation possible (community service hours, courses, fines etc.). If you look to be taking the probation seriously, the PO may cut you some slack for this incident.
It would be wise to consult a local attorney before your next probation visit. S/he will be able to tell you exactly what you can expect. You should be careful making any statements to your probation officer regarding the failed test. Statements to probation officers can often be used against you in violation of probation hearings.
Usually probation officers are not involved with the interlock. DMV is. Also, interlocks can register positive for other substances or sources. I had a client who used mouthwash register positive this week.
The Probation Officer should not find out about the failed BAC. The DMV is the only entity that is notified regarding interlock issues. You may have problems with the DMV and subsequently have your interlock restriction extended due to positive BAC's, but your Probation Officer should not be notified of this issue.
Sign up to receive a 3-part series of useful information and legal advice about DUIs.