Nothing is saved in Account settings When I'm at this page "admin/config/people/accounts" I can't change anything of the settings. So I uncheck a checkbox or typ another value in an input. When I click the save button, the page reloads but the settings go back to the values before. 

Anyone who knows the problem? Other pages does save my settings, it only appears on the "admin/config/people/accounts".

I use Drupal 8.

Thanks!
In modules check for the hook_user_admin_settings_alter, check the form action and change it for the modules implementing those function

$form['#submit'][] = 'module_user_admin_settings_submit';

For reference sample forgot_username module

Instead of this 
$form['actions']['submit']['#submit'][] = 'forgot_username_user_admin_settings_submit';,

use this
$form['#submit'][] = 'forgot_username_user_admin_settings_submit';

In my case, forgot_username module breaks the account savings.

Reference : https://www.drupal.org/project/private_message/issues/2905184
Patch : https://www.drupal.org/files/issues/private_message-admin_settings_submit_handler_beta18-2905184-3.patch