Index page no longer responsive

My index page (landing page) previously was responsive and reacted to all screen sizes (computer, tablet, phone), but now, for some reason, my development version looks different from my live version. I didn’t change anything, and it appears to be that the software has changed since I published to live. Now when I go to the responsive option on the development version, I see “currently in a fixed layout” and “make responsive”, but it seems to react differently than before. Any ideas?

Unsure why that would have occurred, have you made any changes you need to keep since you last published? Can you restore to that version?