Currently, there isn't a way to manually sell to a new customer, so you can't set the start date of that product after a new customer purchased using a checkout link (I,e, ALL new customers). You can't change the start day of an already sold product. Needs to be able to change the start day, or, if at last there will be a way to sell a product manually without sending a checkout link, to set the start date when you sell the product. (this was marked resolved missing the whole point).