There seem to be two different issues in your post: whether meal replacements work, and why hasn't diet/exercise worked for you so far.
To deal with the first one first: yes, meal replacements work for some people. There are different programs and different levels to choose from. If you want to follow the strictest program, like Optislim, where you replace all three meals and end up on a very low calorie program I'd do it only under medical supervision. These programs are designed for people who have a lot of weight to lose and who need to lose it quickly, for instance if they need surgery. Other programs are less strict and only require you to replace one meal per day. Others fall between the two and allow you to decide how many meals you want to replace, or slowly phase you back into incorporating more 'real' meals into your diet.
On paper they should work for everyone because they restrict calories. However, whether it works in real life depends on whether or not you can stick to it, and whether you fall back into old habits once you stop using the meal replacements. Some people can stick to it, others find it's not for them. My MIL lost 20kg using Tony Ferguson. However I know plenty of people who have tried meal replacements and have given up within a week.
If you want to find out if it will work for you first speak to your doctor to find out his or her advice. If, and only if, your doctor says it's okay then give it a go. Sign up for a week or so's worth and see if it works for you. If it does, great. If it doesn't, that's fine. A lot of weight loss is about trial and error to see what system works for you.
As to the second issue, can you give us more details about what you are doing with your eating and exercise? There are several possibilities as to why it's not working:
You may still be eating too much. What people consider average food portions to be has crept up over the years. Check this site out
to see if your portions are larger than what is recommended. Or you can sign up for a free Calorie King
account and use their food planner to check out the exact calorie content of what you eat in a day. If your hour of exercise is walking or other low impact activity it could be stimulating your appetite without burning the corresponding number of kilojoules.
Or you may be eating too little. If you are being incredibly strict with your diet, and that one hour of exercise is cardio where you are burning a lot of calories, you may be getting below 1200 calories per day in total. Once your calorie intake gets below a certain point your body will slow its metabolism and decrease the amount of fat burned during exercise. It does this to prepare from famine because it thinks you are going to starve to death. If you find on Calorie King that you are eating too few calories, or exercising too many away, then the answer may actually be to relax a little. Exercise a bit less, or eat a bit more.
What sort of exercise are you doing? If it's seven days of cardio then you might need to use a different routine. Alternate cardio days with weights/resistance days. Make sure you include at least one rest day your your body to recover. Muscle burns more calories at rest than fat does, so by building muscle you raise your resting metabolism. Or if you always run you might need to substitute a different activity like swimming on your cardio days. The human body becomes efficient to minimise burning excess calories. That's why something like running seems so hard at first, but becomes easier over time. Your body adjusts to make it easy. If your body has adjusted you'll need to either increase your current exercise by doing it faster or for longer (no more than 5-10% increments though or you may injure yourself). Or start doing a different activity which your body finds harder for a while.