For one thing, you can not deliver the cargo to Jose Zugarro because you don't have the cargo! You're supposed to be delivering 960 cwt of coffee and you don't have that much.
You've managed to slip through the various checks against your reputation and relations. Your relation with Spain is -46, which is just low enough that Jose Zugarro normally wouldn't want to talk to you and should say "I refuse to trade with a person of your reputation and relations." But because you have a delivery quest for him, he is willing to talk - he's waiting for you to deliver his coffee. However, he still won't trade with you.
All other store keepers do the same, but your relation with other nations is -45, which is just high enough that they're willing to trade. So you must have done something to annoy Spain and reduce your relation to -46.
You have a ship-hunting quest. Complete that. It should raise your relation with Spain, then Jose Zugarro will be willing to trade. But you still won't be able to deliver the coffee until you have enough coffee! (Once he's willing to trade, you can probably buy the coffee from him, then deliver it to him to complete the delivery quest.

) Note, however, that the target of that ship-hunting quest is British, so sinking the ship will ruin your relations with Britain. Thomas O'Reily will probably not like you after that...