Vault TLS Certificate authentication method - authentication

Question

Recently,I am learning about the authentication related knowledge of vault,and I plan to use the TLS Certificate Auth Method (API), but I have encountered some problems in the process of practice.
I have 4 self-generated certificates locally, clientCA.pem, serverCA.pem, client.pem and server.pem (cn is test.example.com). Here are the steps involved in the certificate.
1: My config.hcl file is as follows
listener "tcp" {
address = "[::]:8200"
tls_cert_file = "/certs/server.pem"
tls_key_file = "/certs/server.key"
tls_disable = false
}
2: Create CA Certificate Role
curl \
--header "X-Vault-Token: $VAULT_TOKEN" \
--request POST \
--cacert clientCA.pem \
--data '{"display_name": "test-ca"}' \
https://test.example.com:8200/v1/auth/cert/certs/test-ca
3: Login with TLS Certificate Method
curl \
--request POST \
--cacert serverCA.pem \
--cert client.pem \
--key clientkey.pem \
--data '{"name": "test-ca"}' \
https://test.example.com:8200/v1/auth/cert/login|jq -r ".data"
When executing the second step, an error will be reported,
curl: (60) SSL certificate problem: unable to get local issuer certificate
Then I log in via rootToken and operate on the Web interface. Created a test-ca role, the imported Certificate is clientCA.pem
When executing the third cloth, an error is reported curl:
(60) SSL certificate problem: unable to get local issuer certificate
When I replace the serverCA.pem in the original command with server.pem, the error
{"errors":["invalid certificate or no client certificate supplied"]}
curl \
--request POST \
--cacert server.pem \
--cert client.pem \
--key clientkey.pem \
--data '{"name": "test-ca"}' \
https://test.example.com:8200/v1/auth/cert/login|jq -r ".data"
When I went to the interface to change the Certificate of test-ca from clientCA.pem to client.pem, the modified curl was executed successfully.
curl \
--request POST \
--cacert server.pem \
--cert client.pem \
--key clientkey.pem \
--data '{"name": "test-ca"}' \
https://test.example.com:8200/v1/auth/cert/login|jq -r ".data".
Now I feel that I don't know the relationship between these certificates, and I have consulted a lot of documents, but I still do not understand it so far. I hope you can help me and provide me with a solution.