Tabs not aligned horizontally, rather vertically. How do I fix it?

This plugin doesn’t render correctly. On some websites the “Click on a tab to select how you’d like to leave your comment” labels are stacked vertically. On other websites the tabs are horizontal. I want it horizontal on all my websites. How do I do that?

It looks right on this site

It looks weird on this site

I have dozens of sites. What’s up?