i need help i don’t know why this problem happen
Is it a freenom domain? If so you can’t add it because that domain is registered under a TLD which is governed by the Freenom registry. Freenom currently experiences issues with their Whois service which prevents such domains from being added to Cloudflare. Freenom needs to fix that on their side. Unfortunately there is no ETA known for that.
It probably is best to register a proper domain instead. They already go for less than $10 a year.
If it’s not a freenom domain, may I ask how many times have you tried to add it?
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