Im trying to use Iced Coffee in one of my recipes, but I'm unable to place it in the cauldron for the recipe. I've used the Brewery:iced_coffee but it won't work for me, even though, I was able to put coffee itself in the cauldron.

So 'Iced Coffee' is your ingredient.

It has to be in the ingredients list, it also has to have be used in a 'cauldron recipe' as per the configs.

You could try 'Brewery:Iced Coffee' to see if that works