Stu is entirely right. People of a larger size can gain/lose 20lbs on a keto/carb up (due to water), but someone your size should not expect such a dramatic shift.
However, I have never heard of someone initially gaining weight when going on keto, due to the drop in water.
What were your kcals before keto?
What does your training look like (I know, we are in nutrition, but I would like to understand the sudden weight gain)?
A piece of advice I have is that, for me personally, switching from cheese to chicken breast and olive oil (of equal or lesser total calories), and getting leaner cuts of beef helped me continue to lose fat when ketogenic and stagnating. While I have always found saturated fat gives you the best energy when ketogenic, too much has (IME) held me back in my fat loss goals.
All the best,