Trouble Assigning with Multiple Courses

Hey everyone, 

First let me say thank you for taking the time to read this and offer help.  I teach at a non profit that helps young adults complete their GED/HiSet.  

My account is using multiple course for math, science and history/govt.   My issue is that when I want to assign something I go to the content page, click on the course listed to bring up the pop up box of different courses, but I can only choose from about 4-5 and cant access the others.  Seems like the pop up window may be limited to showing only 5 classes.