Invalid postcode in Click and Send even after using dropdown list

[kayabread07]

I've just started to use Click and Send, and I keep getting an error saying that the postcode is invalid. I googled the address, checked the suburb, and everything is correct and in the correct "suburb" field.

I used the "Search City/Postcode" button, which populates a dropdown list and I selected the correct suburb. However, I'm still getting the error  that the postcode is invalid! This happened for the 2 items that I'm trying to send out to 2 separate people, and it's driving me crazy. Any help is very much appreciated thank you!!