We recently upgraded (from 2.4) to v2.9, and I enabled Achievements. I imported the default_achievements file. When I solve math problems (from my instructor account), I get pop-up messages with the achievements, but the icons are not displayed - instead, there is text saying "Achievement Icon" on the left side of the pop-up box. I have verified that the image files are in my html directory, and I am able to see the images on the Achievements page and in the Achievement Editor. They're just not showing up when I actually earn the achievement.