payment for my programme that was bought outright

Can you please explain why I have to pay for my product when it was purchased outright. When my son got it for me he paid the full retail price for Photoshop, and installed it in to my computer for me, This was then my property to use as and when I needed to, and this is the version I have been using ever since, so can you please tell me why I have to pay a subscription for a product that has already been paid for. As I am now a pensioner, I just do not have the extra money to spare. But have now lost my enjoyment of doing my artwork, I  also do a lot of art to help our charity work for The Royal British Legion as I do a lot of publicity for our branch in Dover.

Brian Walton