I changed the equipment and my sets disappeared

Changing the equipment on an exercise makes it a different exercise. The sets you logged belong to the old one, so they are removed along with it.

Kovo asks you first whenever there are sets to lose. If you have not logged any sets on that exercise yet, nothing is lost and the change costs you nothing.

The rest of your workout does not change. Only the exercise you touched is affected, and the sets on every other exercise stay as they are.

Learn more: How do I swap an exercise?