Hello Rabbi, do you remember those marshmallows twists for Pesach? They are made by the company in the title of the question. So I checked the Hashgacha on the back of the box, it just said the letter K and then parve under it, but on the front it says Kasher LPesach Rabbi Andrue Kahn. I did research, for Limot HaShana it’s under Kof K, but this Andrue guy is reform, he only certifies Pesach line I guess. On the website of Joyva, they have an article of his explaining why the products are ok to eat for Pesach. In the ingredients there is corn syrup, so it is kitniyot, but he brings a Teshuva of Rav Kook that since it’s a kitniyot derivative it’s not kitniyot (minhag isn’t like this but this won’t matter according to him because of his next point). He also says kitniyot doesn’t apply nowadays because all concerns don’t apply. Now I know this wouldn’t matter for Ashkenazim since minhag Yisrael kehalacha. But could Sephardim eat this product? I don’t know if the reformie is Yotzei venichnas, and even then is he doing that with the Kof-K or no? And I don’t think they make any Chametz products bichlal, but tzarich iyun as they say.

ב"ה Shalom, To be short and to the point. Is is best not to make assumptions with processed food especially candies and treats since production is complex and requires professional knowhow. Since the product is under Kof K supervision all year besides Pessach you should contact them only since they will know best why it did not receive Kosher certification for Pessach. https://www.kof-k.org/ Have a happy and kosher Pessach