Make sure you are actually assigning your employees tasks. For your own piece of mind, don't assign them to ring customers up, though. They fixed a LOT of the employee AI in the last big patch but ringing customers up still has some issues. I usually tell them to restock and if I get a second one, I have them clean (you will be amazed sometimes at how dirty display cases can get). Sometimes their task falls off too. You can berate them for slacking but check their assigned task is still assigned to them because it does happen. Also you generally need to assign them daily (but not always, I always check as soon as they come in).
As for them not buying goods, mine sell like (pardon the pun) hotcakes, even on normal pricing. Make sure the quality is decent, though. I didn't open my bakery until my sim could make excellent or better baked goods and I don't sell anything below excellent quality.
