I did not actually solve the puzzle: I thought I had proved it impossible, and got really curious about the answer.

The problem is that the ring cannot go through the hole, and the rope goes through the hole, so the ring cannot get to the other end of the rope.

It's an optical illusion: the rope does not go through the hole. It goes in, and comes out again.
There's nothing stopping you from pulling this part of the rope through the hole so the ring can go past it without going through the hole.

When you do that it pulls another part of the rope through the hole, so you just need to get the ring past that part first. Then you pull the other part through, and get the ring past that. Then push it back through again.

So the ring is on the other side of the rope, without ever going through the hole.

Kudos to you if you solved it without the answer!
* gives to you a gift of many, happy ducks *