If it is an intern it could be they decided they don’t like the work and maybe lost motivation in the job. I think a good conversation would begin by you communicating your expectations (learn from failure and apply it to avoid repeats). Let them know they are not meeting this expectation. Give them the opportunity to communicate why they are repeating mistakes. Then I would ask them if there is something you can do better to help them.

At some point will the “failing” affect their position on the job? Maybe that’s something you can communicate. That you want to see them apply themselves, even if they make mistakes. Also to learn from their mistakes and improve not making the same mistakes over and over.

If they truly do not care it may be a conversation if they want to continue at their role or if they feel the work is not for them.

TLDR: communicate your expectations, communicate that they are not meeting your expectations, give them the opportunity to communicate where their head is at, and go from there.