It sounds like you’ve been keto for a few months, so it doesn’t sound like your insulin is the issue (a lot of people, myself included, have a very difficult time with weight loss due to insulin resistance, and fasting takes time because of this).
So it’s one of two things:
Your re-feed. You might be getting in more than you’re burning in a large binge. It’s hard to do this when Keto, but I’ve seen it happen. What’s your re-feed like?
Everybody (and every body) has a set weight point. This is the weight point that everyone naturally gravitates towards and that the body will constantly try to regulate towards. There have been some interesting speculative studies based on this idea and fasting is showing promise at slowly moving your weight downwards, re-regulating your set weight point to a lower number over time.
If you constantly go back to the same weight range (within five pounds) your body might be trying to regulate back to this range. Bodies are actually really phenomenal at regulating themselves and it will find a way to hold onto that fat store to the best of its ability…but it can’t do it forever. Fasting repeatedly will eventually lower this and you’ll start seeing progress, but it might take more time than you’d like to see.
So if your re-feed is fine (I’d make sure to track it/keep a food journal to make sure nothing is adversely affecting you/your re-feed isn’t too high) it might just be a load of water or your body trying to maintain. You’ll likely see a woosh (large weight loss) if you stick with it! It doesn’t sound like you’re doing anything wrong. Sometimes it just takes time.