Finding/removing old cloudflare account where logon has been lost?

We’re in the process of moving a client with a domain to Cloudflare. This is the first time we’ve ever dealt with domains and turns out the registrar does a pre-check before redelegating to make sure the DNS servers are responding correctly.

We seem to have found a bug/problem between the registrar and Cloudflare - the Cloudflare servers are returning records that indicate the DNS was hosted with CF in the past and is still returning those old records so the re-delegation is being denied

The client doesn’t have that logon and we need to remove that old Cloudflare instance before we can get the domain delegation done and pointed to the new Cloudflare account

Any ideas how we can do this?
In the past we’ve seen inactive domains on Cloudflare be auto-removed but doesn’t look like it’s happened in this case

What you will want to do in this case is temporarily revert your name servers to your original, non-Cloudflare, name servers. Once the other name servers take effect, you can then use new CF name servers from a new account and it should work.

They’re already pointing to non-Cloudflare servers and have been for years
now but seems the old domain hasn’t been removed from the old account.

The problem is the registrar does an nslookup against the new
servers before delegating querying them on who the nameservers are for the
domain. When it does this CF is returning the old CF nameservers