Sounds like you may have enabled Guided Reading Mode while assigning the text. This causes the text to be blurry for students. Here's a quick video to introduce you to this CommonLit Digital feature! Click on the link to view the video.
If you didn't mean to enable Guided Reading mode, you can disable it by editing your assignment. If you meant to enable it and students are confused, be sure to explain for them how the tool works; you can use this video as a guide: