As Nancy said, it's not what exercise you do, but THAT you exercise that will help you along. But weight loss is more in the kitchen than in the gym.
So balance your running and gym classes in whatever way makes you happy. :)
The question is - if you're new to these, did you update your fitness goals on your spark fitness settings? If you didn't and you're still eating as per old goals, that might be why you're not losing.
How long has your weight stayed the same? It's normal for weight loss to not really kick off for up to 6-8 weeks after starting a new healthy lifestyle.
Deb, in New Zealand