DNS from old account Cloudflare, can I change?

I work on a new project and I have created a new Cloudflare account and trying to add a new dns but I have an error "“Name server not valid”. I have read an old dns and it’s the other, but closed/not used, account Cloudflare. Can I have delete the old DNS? Thanks
I have tried to close zone and come back website to original DNS (by Aruba) and starts again but not works.
Can you give me some suggestion?

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