One of the biggest hassles, when you make popcorn, is when you are left with un-popped kernels. You can’t wait for them to pop because if you do, the ones that are already popped will begin to burn and no one wants that. But, do not just automatically assume that it is the fault of the machine that you are using. There is actually a plethora of environmental factors that can come into play.
The freshness and moisture content of the kernels themselves can be as much an issue as anything, as will be discussed in a bit. If the kernels have not been stored in an airtight container at room temperature, you may want to avoid using them.