What should I do when I'm on financial aid probation?

Okay I got a letter in the mail saying I'm on financial aid probation telling me that my GPA has dropped to a 1.47. I tried to sign up for classes but its not letting me. I'm going to call them and ask what I need to do but is the reason why I can't sign up for the classes I need because my GPA is a 1.47? I've never been this stressed out in my life.