probation violation this is the second violation this time it was for missing an appoitment? what are the chnaces of probation being revoked

It depends on the probation officer and the judge.  I would call the probation officer as soon as possible and attempt to resolve the issue before a formal petition to revoke is filed, or, if the petition has already been filed, before the court date. You may also want to check with the attorney who represented you in the underlying case.  He or she may have some familiarity with the probation officer or judge or both; and have some sense of how best to deal with them. For the future:  Buy a small pocket calendar and start writing down all of your appointments whether with probation or otherwise.  Making and keeping appointments is an important skill that will serve you well in many circumstances.  Best of luck.