Purolator accounts and/or Production Keys are typically set up to only support shipments originating from the account’s registered address. This is a security measure imposed by Purolator that it refers to as the Sender's Address Restriction.
If you define warehouses or drop ship locations with postal codes that differ from the account's registered address, you may get a message informing you that no shipping rates are available. In this case it's likely that Purolator has the Sender's Address Restriction enabled on your web services production key.
Contact Purolator (888-744-7123) and ask to have the Sender's Address Restriction removed from your web services production key. This should resolve the issue.