Placing block from a module not working I've followed the tutorial to create a custom block from
https://www.drupal.org/node/2101565

My module installed fine and I can see the block in the list of available Blocks for placing, but as soon as I click "Place Block" I just see the ajax loader for about 1 second and then nothing happens, the dialog stays open and my block does not get placed. Cleared the cache etc. didn't help, the error log does not show any available messages.

My src/Plugin/Block/TestBlock.php file:

&lt;?php
namespace Drupal\test_block\Plugin\Block;

use Drupal\block\BlockBase;

/**
 * Provides a 'Demo' block.
 *
 * @Block(
 *   id = "test_block",
 *   admin_label = @Translation("A Test Block"),
 * )
 */
class TestBlock extends BlockBase {
  /**
   * {@inheritdoc}
   */
  public function build() {
    return array(
      '#markup' =&gt; $this-&gt;t('Hello, World!'),
    );
  }
}
?&gt;


Drupal 8.1.1
You have an error in your block that causes a fatal error or exception.

Right click and open the place block in a new window and/or check your error logs.