Indesign Interactive PDF not saving progress of buttons clicked or elements activated.

I have created a subject selection guide for students at my school. This guide has Yes / Maybe buttons next to each subject however when I save the PDF after selecting some of these 'yes/maybe' options and reopen the PDF, all the buttons are reset to their primary state. The only way I can get them to stay selected is by re-exporting the PDF but this will be problematic for our students. Why does clicking a button not register as a change to a file which would allow CMND S to overwrite the file? Anyone know how to make this happen? Thank you 😉