I searched the theme’s header.php but only found one instance of <header id=”masthead”…
I see the duplicate masthead ID too when I view the page source in the developer tools console for that page.
Any suggestion on where else I might track down the source of the other ID causing the problem?
BTW, I also tried
body.page-id-946 #masthead {
display: none;
}
but that did not work.