I have no idea how old the OP is, but I put on weight after the menopause and had just the problems that the OP has described. In my case only put on a stone and a half, but allowing for the time it took me to gain the weight - about 5 years, for 15 years after that, nothing I did could shift the weight. Like you, the eat less, exercise more mantra got me nowhere. I tried every kind of diet. I even tried the Atkins Diet, which made me very ill but left my weight static.
Then about 15 years later, when I reached about 70, something changed, all of a sudden I had another go at loosing weight - and it went. I lost weight on the original 5:2 diet, but I do not think it was the diet I used that made the difference.
My theory is that the once hormone turmoil and changes of the menopause finally ended and the levels stabilised, my body returned to a state where weight loss was again possible. I say that as someone who had an almost symptomless menopause, so I do not think it a function of whether you had an easy or difficult menopause, but I think the hormone changes and disruption affect our ability to regulate our weight much longer than we realise and for some of us it leads to a weight gain we find very difficult to shift.