Why is MailStream Plus not giving DNDC (NDC Destination Entry Discount) rates to offshore Letters/Flats mail.

MailStream Plus, all versions, all platforms
USPS Labeling List L601 for NDCs has the following note:
"Mail for the following Zip Code ranges is not eligible for DNDC discount prices: 006-009, 967-969, and 995-999, except as allowed under DMM 256.2.17, 256.2.18, 266.4.3, or 705.6.4.1." 

So off-shore mail such as to Hawaii (3-digit 967 and 968) is not normally eligible for DNDC rates when taken to the NDC.  Which in this case would be "NDC SAN FRAN CA 94850".

The exceptions referenced in the above L601 quote are found in the Domestic Mail Manual (DMM), and mostly have to do with certain types of Parcel mail pieces.

L601 quote with DMM references is as-of Nov 1, 2017
UPDATED:  November 1, 2017