Payment Gateway page is blank

get the following error:

Fatal error: main() [function.require]: Failed opening required '/home/username/public_html/billing/modules/gateways/gocardless/GoCardless.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/username/public_html/billing/modules/gateways/gocardless.php on line 0

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please help