Squid 503 error. Unable to forward this request at this time.

При работе прокси возникли траблы - не хотела через себя пропускать траф - такая ошибка

ERROR
The requested URL could not be retrieved
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While trying to retrieve the URL: http://example.com /

The following error was encountered:
Unable to forward this request at this time.

This request could not be forwarded to the origin server or to any parent caches. The most likely cause for this error is that:
The cache administrator does not allow this cache to make direct connections to origin servers, and
All configured parent caches are currently unreachable.
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Как оказалось IP этой прокси был забанен в iptables и все пакеты дропались. Убрал правило из iptables - все заработало.