Not sure what you mean by getting soft. Stems rotting? Wilting that is not a result of lack of water is usually due to overwatering/soil saturated/roots rotting. Does the pot have drainage holes? Is the plant in a pot that is set within another pot that doesn't have drainage? Ivies need bright light - not necessarily direct sun, and not in extremely low light. They should be watered when the soil is dry to touch. I suggest you knock the plant out of the pot and look at the root system. If the roots are stringy, brown or dark in color and soft, they have rotted. You could take cuttings and root them to save the plant. But if the roots are damaged it's a lost cause.