I'm trying to swap between 2 material attributes in a Master Material through a Blueprint but I'm getting an error.

I have a MPC that links to a Blueprint that checks the value and displays something. In my case, I have it set up so that when the value is 1, and the Data Asset for my level is set to Rainy Weather, it displays puddles, and when it’s 0 and the data asset is set to Snow Weather, it slowly covers the area with snow. I’m using a Switch for this transition and I’m getting an error.