J.T.
I have never tired them - read to much about scams etc. But I found when I couldn't lose weight that there was a lot of "hidden" calories that I could take out (extra hand full of nuts or extra piece or two of fuit etc.). Also although I was exercising I was not exercising correctly to maximise weight loss. There are charts on heart rates, and aerobic heart rates and what you should be trying achive for the maximum efficacy of your workouts. You do not say what you do for exercise, bu hopefully it is aerobic since that is the best for weight loss and overall health.
Also - please don't take this the wrong way - Being a vegan does not mean you eat healthy, it just means you don't eat meat dairy etc. Portion size and the amount of fat / calories you take in are what decides whether you lose or gain wieght, whether the fat comes from a cut of meat or nuts doesn't matter to your body, once it has what it needs, it stores the extra.
You might want to see if your Doctor has a mchine to measure your metabolic rate (I forget what it is called). THis will help them determine how many calories your body needs to function. From there they can help you determine how many calories you should be eating over the course of a day.
Good luck!