Ivy is a difficult plant to get under control and it can take some time to be fully rid of it. This plant has a very tough leaf and stem, which can be difficult to achieve enough absorption and uptake of the weedkiller to have a lethal effect.
Treat new, young growth where possible as this will be more vulnerable and gently bruising the leaves before application by brushing the leaves with a stiff brush or with your fingers, will aid uptake of the weedkiller. After spraying, do not be tempted to remove the top growth until it has fully died back. Apply the weedkiller efficiently and repeat at approximately 4-week intervals until the area is clear.