Hi @youngjo. Thanks for being part of GoDaddy Community! It would be hard to say what is happening without more information. If you have successfully pointed your domain toward Cloudflare and you're getting an error, the best thing to do would be to reach out to Cloudflare's support so they can investigate the issue. If you'd like to share the domain here along with some more details, someone else in the community might also be able to suggest a solution. Hope you're able to figure this out!
JesseW - GoDaddy | Community Manager | 24/7 support available at x.co/247support | Remember to choose a solution and give kudos.