Very small images

I think this is a very simple question but I can’t work it out. How should I be outputting this image from an image field? Currents it outputting a very small size

    $articles = page('articles')->children()->visible();

<?php if($image = $article->thumbnail()->toFile()): ?>
   <?= $image->imageset([
      'sizes' => '(min-width: 640px) 100vw, 50vw'
   ], [
      'class'      => 'project-thumbnail',
      'placeholder' => 'blurred',
   ])->html() ?>  	    
<?php endif ?>


    label: Thumbnail
    type: image

Have you installed the plugin properly with the CSS and JS files in place?