I couldn't say, I'm down to 30kg. The shakes aren't magic though. The average woman needs 2000 calories a day to maintain weight, so to gain you might need even more. The Ensure that I have is 300 calories per bottle. So if you're drink 2 a day, they're providing you with 600 calories - which means you still need to take in plenty more from food to make sure you're getting over 2000.
I know there have been times where I've been forced to realise that eating a lot more than I used to does not mean I'm eating enough to gain weight. For example, if I add in a couple of extra snacks, I trick myself into thinking, I'm eating more, therefor I'm doing enough, when actually even though I am getting in more calories than previously, I'm still not meeting the amount I'd need to gain.
Another thing I've found is that feeling ill can make a small portion of food seem bigger than it actually is. When I am already feeling stuffed or sick, facing food is so hard that even a small meal looks like loads to me. And when you're feeling ill, you can feel so awful and full after eating even a small meal, that you end up convinced you've eaten a lot because you feel so stuffed, you can't believe it was actually a small portion.
Another possibility is that you are not absorbing food properly, so you may be taking in enough calories but your body is not able to use them.
Have you tried counting calories? Work them out for a few days (you may need to weigh your portions to be accurate, and you can find guides to the calorie amounts of various foods easily online). Then work out an average. It may reveal that you're not eating as much as you think. Or it may reveal that you are eating enough - in which case you should probably talk to your doctor about the possibility of malabsorption.
