An interesting thought exercise is to compare a retail suit and a tailor made suit. One can be purchased and returned for a full refund, while the other one cannot. Although both are tangible, the tailor made suit is also a service which in this example was already rendered when the suit was tailored.
Products and services cannot be defined by saying that one is the opposite of the other (as the concept isn’t binary). As a result the requirements to sell services online are radically different from products, especially on a marketplace.