Changes to buttons not saved?

When I edit my buttons, I then click “Save.” The screen refreshes and the old settings are back. I’m clicking the blue button that says “Save”, under the tab that says “Button.” I also tried the blue button that says “Save” at the bottom of the page. Why can’t I edit my buttons and save the changes? I’m editing the URL field and the Text field. I’m using MaxButtons 1.37 (free version) and WordPress 4.1.1.

https://www.ads-software.com/plugins/maxbuttons/