Microwave popcorn
Since you have bought popcorn for the microwave, kept exactly to the Watt specification, etc. and still a large part of the grains is not popped up?
You can try this trick: put a plate upside down in the microwave and place the popcorn bag on top. With us it works so well that almost 100% of the grains explode.
One advice that I personally have not tried yet is to keep the corn kernels in the freezer. Supposedly this should keep the wall of the cores stable? a requirement for "poppen". With us the Tellertrick works, but also that would be worth a try.
