为什么我的扩展文本大小的辅助功能工具不起作用？

I'm adding an accessibility tool of users being able to increase the font-size of all the text on the page, and being able to go back to the default font-size if they wanted to. I have made a second CSS file which holds the css rules for the text to increase. However when I click on the icons I made for the text larger/text smaller it does not work. Can anybody understand why? Thanks for the help.I'm adding an accessibility tool of users being