Drupal 8: Mismatched entity and/or field definitions

Thanks to: https://www.fuelforbrain.com/drupal-8-mismatched-entity-andor-field-definitions

• If you don't have Drush for drupal 8, please add the following script before $response->send(); in index.php file(located in Drupal root folder) and reload the web page.

try {
  \Drupal::entityDefinitionUpdateManager()->applyUpdates();
}
catch (EntityStorageException $e) {
  print_r($e);
}