You should immediately inform your probation officer of your illness and inability to work, and you should provide your probation officer with the medical evidence that is necessary to substantiate your disability.

Courts accept that people have health issues, and it is common for courts to extend probation or make similar allowances when a crisis occurs -- but courts and probation officers want to know what is happening before somebody violates probation, not after. If you don't address the issue up-front, the court may not be anywhere near as receptive to your claim of disability made after you're eventually picked up and brought back to court on the probation violation.

If you are so ill that you also cannot attend required meetings with your probation officer, that's an issue you should also address before missing any appointments.