If your snake doesn't eat for a few week, it's ok and stop switching foods. My pastel didn't eat for 13 months. Yes there is some weight loss but not very significant. You just have to monitor the weight.

If after a few month of fasting, you can then start feeding a mouse or african Soft fur rat just to get it started and continue feeding its original food prey. The time you wait before taking action depends on the weight of the snake.