Many decorators on CD use this, hopefully someone will weigh in with some helpful information. You said it was rainy and humid, which if anything, would most definitely make your fondant soft.
I occasionally buy coloured virgin ice fondant. I bought a batch of red that was so nasty, I returned it. Totally unuseable. Was hard, like concrete, couldn’t even knead it. First time I returned fondant. Figured it was a bad batch. That can happen. I would definitely contact the company you purchased it from for a refund. I’d also contact Carma Massa Ticino directly. Let them know how disappointed you were with the product. What happened, and how inedible it was, and you had to refund the bride. Look on the tub and include the batch number and date. Then they should be able to track it. Who knows, maybe the tub the seller sent you was a really old batch??
Creativity is God's gift to us. Using our creativity is our gift back to God. Clarky's Cakes 😎