Anonymous participant - Ok, because if you were in the southern half of the country, you would have had to go through the consulate in HCMC. It most likely was canceled because something that was entered into the online application was entered incorrectly. The platform is notorious for making mistakes inputting your details, after it pulls the data from your bio page pdf. Name misspelled, middle initial versus full middle name, etc. often something very little, can can a cancellation.
Passport place of issue is Japan, if you have a Japanese passport. Some applicants who renewed their passport overseas have been canceled if they list the country where they were physically when they renewed.
Cancelation is usually do to an issue with the application. Where are you located when you applied via the Hanoi embassy? Any possibility that you entered your name or datapoints incorrectly? Another one that seems to trip applicants is if they renewed their passport while overseas, listing the country where it was renewed as the country where the passport was issued, when the e-visa wants you to list the country of the passport.