The only way to access your fat stores is to drop your insulin. You cannot access fat with insulin in your bloodstream because it is designed to make your body hold on to fat.
To drop insulin, you have to remove carbohydrates from your food as that is the trigger for insulin. This is why the carnivore/paleo/keto diet works. It drops the insulin through the floor. You can eat fatty meat and eggs etc and you lose the fat because the insulin is down, your pancreas is having a rest and you start to burn your own fat to fuel your body.
Calories in, calories out works up to a point but if you are not losing the stored fat, it's because the veggies and carbs etc. that you are eating, even in tiny amounts, is triggering your insulin and you are in fat storying mode.
When you start to remove the carbs, you use the carbs in the form of glucose from you bloodstream first, then you use the stored supply in your liver (that is held there to manage the bits between meals) and when that is depleted, you use the long term storage your body has built up. This is when you go deep into ketosis and really start shifting it.
A bit of intermittent fasting along the way will accelerate it but don't overdo it as it will make you feel rotten until your tissue is 'fat adapted' i.e., it can burn ketones really easily.
Anybody on a vegetarian diet that can't lose weight, needs to look at store cattle or overwintered sheep. They feed them vegetable matter to get weight on them for market or for the next round of pregnancies. Animals that eat 98% low carb, leopards, cheetahs etc., have very little stored fat.
Animals that can only eat low carb food but still gain weight, such as seals, have to catch their food but lie about doing nothing in between in order to keep that fat stored on their body.
Look to what you are eating that is releasing insulin @Sorryagain , remove it in favour of foods that do not and you will shift the stored fat. A bit of intermittent fasting will accelerate that and remember that you don't really start to properly burn it until the stores are depleted from your liver so three or four days.