24-105 Error 101

I had Err01 recently on my 24-105 - fortunately at the end of a trip- and it needed a repair (new ribbon inside I think) costing about NZ$180. If you check the forum you will see that quite a lot of people have this issue with this lens after 3-4 years. It works fine again now and came with a warranty for three months on the repair.

It's very likely to be the same problem. Up to you how you deal with the new owner but it's just someone's bad luck...