Error while try to enable cloudflare for domain name???

I have added my domain into cloudflare, but when try to enable or disable cloudflare for a domain name in dashboard then received a message like that

“CLOUDFLARE ERROR : No user_key.”

How to fix it?

Do you already have a Cloudflare account with your domain in it (perhaps created by a different hosting provider)? If so, you will need to delete that first before you can enable Cloudflare with us.

Also, note that subdomains and Cloudflare do not work together.

The Cloudflare integration is still a bit experimental and has some problems. For the best results, signing up for Cloudflare yourself and manually adding your domain there is still the most reliable option.