I have been able to search for content in the Cloud in Maple T.A. 2017 - e.g. searching for Distribution gives any folder with 'Distribution' in the title, as well as questions containing 'Distribution' in either the title or the question text. Can also use * to search the start of words e.g. searching Geom* will give you results for Geometry and Geometric. However I'm afraid I don't see the Fourier series folders you are referring to (either in the list or by searching).
EDIT: Also if you are looking for a specific topic, try the "Subjects" list under Maple Cloud, instead of "All Content Types".