I received rejection '033 Invalid DDPP'. What does it mean?

I received rejection '033 Invalid DDPP'. What does it mean?

Port of Unlading Code data element contains a code that does not appear in the Census Schedule D Port code list.

or  

Port of Unlading Code data element is missing

or  

When Message Code data element is 4, 9, U or Y the Port of Unlading Code data element is missing.

or  

U.S. Port of Destination data element is missing or contains a code that does not appear in the Census Schedule D Port code list.

or

When Message Code data element contains code 1, 2, 3, 4, or Z the Port of Arrival data element contains a code that does not appear in the Census Schedule D Port code list or is not a valid In-Bond destination.

or
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Port of Unlading Code data element submitted does not match the Manifest on file (Combination of these 4 elements: SCAC, Conveyance ID, Manifest sequence number and voyage number)