Hi Andrew,
If its an issue with the widget you can try using a normal text box widget and jquery to click the search button when the enter key is pressed. You need to use the html/javascript snippet widget and add this script in it (make sure jquery is enabled).
$(".text-box-class input").keyup(function(event) {
if (event.keyCode === 13) {
$(".btn-search").click();
}
});
replace text-box-class with a class from your text box and replace btn-search with a class from your search button.
Here is a link to the html/javascript snippet
https://appstore.home.mendix.com/link/app/56/Mendix/HTML/-JavaScript-Snippet
Hope this helps!