I use the following command to create your private key and CSR (using the ECC algorithm):

openssl ecparam -out ECC.key -name prime256v1 -genkey -noout
openssl req -new -key ECC.key -out ECC.csr -sha256 -subj "/C=VN/O=Custom Organization/OU=Custom Organizational Unit/CN=*.domain.tld"

After creating the CSR and the private key, I conducted a TLS certificate signed by Cloudflare to install on the original server. But when I check the SSL certificate on this site: Certificate Key Matcher.

When I Check if a Certificate and a Private Key match use the certificate created by Cloudflare and the private key I created above, the result is: The certificate and private key match!

But when I Check if a CSR and a Certificate match use the Certificate created by CloudFlare and CSR that I created above, the result is: The certificate and CSR do NOT match!

Why happen this problem? Is Cloudflare CA didn't use the information in my CSR to build a certificate?