One specific user can't see certain action buttons

I have one specific user who can’t see specific buttons. When I log in as him, I can’t see the buttons. If I log in as another user, with the exact same permissions (Same role, same profile, same permission sets), I can see the buttons.

I’ve verified the rendering conditions in both the page editor and in the XML.

What does the button do?  I’ve found, for example, that a button to Edit will disappear if the user doesn’t have Edit access to the object in Salesforce.