Users are redirected to homepage instead of wp-admin

Yeeey, I figured it out! Actually my theme had a redirect like this one in functions.php:

// Block Access to /wp-admin for non admins.
function custom_blockusers_init() {
  if ( is_user_logged_in() && is_admin() && !current_user_can( 'administrator' ) ) {
    wp_redirect( home_url() );
    exit;
  }
}
add_action( 'init', 'custom_blockusers_init' ); // Hook into 'init'

All you have to do is add your own role capability, for example: !current_user_can( 'manage-reports' )

This helped me a lot.