Make sure your raw stevia was specifically for baking and measured cup for cup with sugar. (busybuthealthy.com)
The biggest thing to note is that gluten - free flours vary in density and can not be substituted cup for cup with regular AP flour. (mindbodygreen.com)
If it wasn't something that measures cup for cup like regular sugar that may have been the reason. (ibreatheimhungry.com)