My Yehuda Matzos box here says “Box should be opened before Shabbos and Yom Tov.”
What if it is the first night of Pesach, and also Shabbos or Yom Tov, and an unopened box is the only one you have? Can you open it, what is the Halacha?
I don't see any reason why the mitzvah of eating matzah would be docheh (override) melachah. Instead, the solution would be to rip/cut the box open in a way which renders it unusable (without ripping through letters/words, of course). Contact your LOR about what way of opening it would render it useless.