Student Name Repeatedly Showing Invalid on Apple Classroom

I am a school administrator. We are using Apple Classroom 2 in a student owned iPad environment. For the most part AP2 is working great for all of my students. However, I have one student who is running iOS 10.3.3, The iPad model she's using is iPad Air 2. This student's iPad continues to show up in my classroom as "invalid". This "invalid" shows up where her name should be. If I delete her from the class and have her rejoin, her name shows up just fine, but then the next day when she comes to class, she shows as "invalid" and I can't access her device. Does anyone have any suggestions how to fix this? All of her settings look the same as other students, and the others are working just fine.