Climbing shoes can be made sticky again by using a shoe goo. This is a substance that climbers use to make their climbing shoes sticky again. It is usually applied by rubbing it into the outer surface of the shoe and then wiping off any excess.
There are also other ways that you can make your climbing shoes sticky again, such as using different substances like petroleum jelly or even soap and water.
These substances will work similarly, but they will not last as long and may not provide the same level of grip.