Hi @amcclung 
Welcome to the Canvas Community. Thanks for posting your question. If your "+ People" button is grayed out, go to your course "Settings" and check the course start/end dates. You may need to temporarily modify those dates so that the current date falls within the start/end date. If you are unable to change the dates on your own, you may need to speak with someone at your school such as your local Canvas administrator or someone in your school's Online Learning / eLearning department. If you can change the dates yourself, you can then change them back to what they originally were after you enroll people in your course.
I hope this helps, Amanda. Sing out if you have any other questions about this. Take care...stay safe...be well.
