Registration Fluid Issue

I am experiencing an issue with a fluid registration setups, I have seen some students unable to move forward with selecting a course for registration. The arrow to continue their registration is not there- it is disappeared. I am including below an image, with the aforementioned arrow circled. Has anyone else experienced this?

Below is what I have received from the user, when the arrow was not apparent:

"  You’ll see to the far right of the screen, an arrow was not showing next to the “Open Seats” column to allow student to select the course and proceed through the registration process. This was the case for her on both Firefox and Chrome browsers. An advisor had to complete the enrollment for her. "