We'd need a little more information to help identify the problem.
Do you know what rule is causing the block? If so, can you share that portion of your rules with us?
I am not sure I can, as this is a client of mine. But I just noticed there are "Rules" that are IP based (not domain based). I think that is the direction for research. Can you point me to online documentation about the Rules, and how Web Gateway processes thru the 'cycles'.