Save Page Button Missing

I have searched for posts on this problem, but all posts seem to be a couple of years old and are of course closed.

I have been working on a new page for the past hour or so, and suddenly the “save draft” and “publish” buttons are missing from the “page editing” page. The two buttons still appear on the “edit post” screen. I have disabled all plugins, but this has not changed anything. Does anyone have any suggestions to rectify this?