Я не в курсе means that I don't know anything about that. It doesn't mean that you don't understand just don't know anything about that, because nobody kept you posted on something or you had been out of the loop or never heard of that etc

Example:

- Почему наш босс такой злой сегодня?
- Я не в курсе = я не знаю

- Что Татьяна делает завтра?
- Я не в курсе

And blah blah blah

Hope it helps