500 Server error in HelpScout API.

gistfile1.php

<?php

try {
  $hs = ApiClient::getInstance();
	$hs->setKey('REMOVED');
	$customers = $hs->getCustomers(1, null, null, null, 'user@domain.com');
		
	// found a single customer for this email address
	if ($customers->getCount() == 1)
	{
		$customer = reset($customers->getItems());
		$customer->setBackground("Edited from the API");
		$hs->updateCustomer($customer);
	}
} catch (Exception $e) {
	print_r($e->getMessage());
  exit;
}