Get "No values found" notice

Hi, I was able to add my first set of Characteristics which is colors with no problem, however, I am unable to add a set of sizes. I added them and only get the label which is Length: and then next to it, it reads "No values found". I'm new to this so probably just missing something.

You need to add both at the same time. Otherwise, the system does not regenerates automatically the variants. In that case, you need to delete the variants of the product, delete the characteristics, save the product and add the characteristics back and the system will regenerate automatically all the variants of your product.