OpenLDAP certificate issues

I wrote a small program to test the OpenLDAP API using TLS or SSL with a local server I made. Everything is in a CentOS machine.

The server has self signed certificates and the option "olcTLSVerifyClient: demand".

In my program and using ldapsearch I can bind to the server without any problems when using ldap://localhost.

With SSL:
When I try ldapsearch with ldaps://localhost I'm getting the error below:

$ ldapsearch -W -H ldaps://localhost -D "cn=admin,dc=local_server,dc=com" -b "ou=users,dc=local_server,dc=com" "uid=testuser"
ldap_sasl_bind(SIMPLE): Can't contact LDAP server (-1)

And on my test program ldap_sasl_bind_s fails with:

Can't contact LDAP server

Test program:

int main() {
    LDAP* session = nullptr;

    std::string sever = "ldaps://localhost";
    std::string bind_dn = "cn=admin,dc=local_server,dc=com";
    std::string bind_password = "1234";
    int version = LDAP_VERSION3;
    int result = LDAP_OTHER;

    // PREPARE CONNECTION
    result = ldap_initialize(&session, sever.c_str());
    if (result != LDAP_SUCCESS) {
        std::cout << "ldap_initialize failed" << std::endl;
        std::cout << ldap_err2string(result) << std::endl;
        return 1;
    } else {
        std::cout << "ldap_initialize returned success" << std::endl;
    }

    result = ldap_set_option(session, LDAP_OPT_PROTOCOL_VERSION, &version);
    if (result != LDAP_OPT_SUCCESS) {
        std::cout << "ldap_set_option failed" << std::endl;
        std::cout << ldap_err2string(result) << std::endl;
        return 1;
    }

    // BIND TO SERVER
    struct berval *admin_cred = ber_str2bv(strdup(bind_password.c_str()), 0, 0, nullptr);

    result = ldap_sasl_bind_s(session, bind_dn.c_str(), LDAP_SASL_SIMPLE, admin_cred, nullptr, nullptr, nullptr);
    if (result != LDAP_SUCCESS) {
        std::cout << "admin ldap_sasl_bind_s failed" << std::endl;
        std::cout << ldap_err2string(result) << std::endl;
        ldap_unbind_ext_s(session, nullptr, nullptr);
        session = nullptr;
        ber_bvfree(admin_cred);
        return 1;
    } else {
        std::cout << "admin ldap_sasl_bind_s returned success" << std::endl;
    }

    ber_bvfree(admin_cred);
    ldap_unbind_ext_s(session, nullptr, nullptr);
    session = nullptr;
    return 0;
}

Wtih StartTLS:
When using ldapsearch:

$ ldapsearch -W -H ldap://localhost -D "cn=admin,dc=pablo_local,dc=com" -b "ou=users,dc=pablo_local,dc=com" "uid=testuser" -Z
ldap_start_tls: Connect error (-11)
   additional info: error:14094410:SSL routines:ssl3_read_bytes:sslv3 alert handshake failure
ldap_sasl_bind(SIMPLE): Can't contact LDAP server (-1)

On my test program ldap_start_tls_s fails with:

Connect error

Test program:

int main() {
    LDAP* session = nullptr;

    std::string sever = "ldap://localhost";
    std::string bind_dn = "cn=admin,dc=local_server,dc=com";
    std::string bind_password = "1234";
    int version = LDAP_VERSION3;
    int result = LDAP_OTHER;

    // PREPARE CONNECTION
    result = ldap_initialize(&session, sever.c_str());
    if (result != LDAP_SUCCESS) {
        std::cout << "ldap_initialize failed" << std::endl;
        std::cout << ldap_err2string(result) << std::endl;
        return 1;
    } else {
        std::cout << "ldap_initialize returned success" << std::endl;
    }

    result = ldap_set_option(session, LDAP_OPT_PROTOCOL_VERSION, &version);
    if (result != LDAP_OPT_SUCCESS) {
        std::cout << "ldap_set_option failed" << std::endl;
        std::cout << ldap_err2string(result) << std::endl;
        return 1;
    }

    int opt_cert = LDAP_OPT_X_TLS_ALLOW;
    result = ldap_set_option(session, LDAP_OPT_X_TLS_REQUIRE_CERT, &opt_cert);
    if (result != LDAP_OPT_SUCCESS) {
        std::cout << "ldap_set_option failed" << std::endl;
        std::cout << ldap_err2string(result) << std::endl;
        return 1;
    }

    result = ldap_set_option(session, LDAP_OPT_X_TLS_NEWCTX, LDAP_OPT_ON);
    if (result != LDAP_OPT_SUCCESS) {
        std::cout << "ldap_set_option failed" << std::endl;
        std::cout << ldap_err2string(result) << std::endl;
        return 1;
    }

    result = ldap_set_option(session, LDAP_OPT_X_TLS_CACERTFILE, "/certs/cacerts.pem");
    if (result != LDAP_OPT_SUCCESS) {
        std::cout << "ldap_set_option failed" << std::endl;
        std::cout << ldap_err2string(result) << std::endl;
        return 1;
    }

    // START TLS
    result = ldap_start_tls_s(session, nullptr, nullptr);
    if (result != LDAP_SUCCESS) {
        std::cout << "ldap_start_tls_s failed" << std::endl;
        std::cout << ldap_err2string(result) << std::endl;
        return 1;
    }

    // BIND TO SERVER
    struct berval *admin_cred = ber_str2bv(strdup(bind_password.c_str()), 0, 0, nullptr);

    result = ldap_sasl_bind_s(session, bind_dn.c_str(), LDAP_SASL_SIMPLE, admin_cred, nullptr, nullptr, nullptr);
    if (result != LDAP_SUCCESS) {
        std::cout << "admin ldap_sasl_bind_s failed" << std::endl;
        std::cout << ldap_err2string(result) << std::endl;
        ldap_unbind_ext_s(session, nullptr, nullptr);
        session = nullptr;
        ber_bvfree(admin_cred);
        return 1;
    } else {
        std::cout << "admin ldap_sasl_bind_s returned success" << std::endl;
    }

    ber_bvfree(admin_cred);
    ldap_unbind_ext_s(session, nullptr, nullptr);
    session = nullptr;
    return 0;
}

What could I be doing wrong in the server configuration or with my code in the test programs?
I want to have the certificates being correctly used specially in the test programs with the OpenLDAP API.