The certificate is not correctly signed by the trusted CA

[kubera]

Hi iam trying to implement native ota example to azre iot hub. I generated ca certificate from https://www.sslforfree.com/

but iam stucked with this error.

..........................................................................................................................................................
E (9482) esp-tls: mbedtls_ssl_handshake returned -0x2700
I (9482) esp-tls: Failed to verify peer certificate!
I (9482) esp-tls: verification info: ! The certificate is not correctly signed
by the trusted CA

E (9492) esp-tls: Failed to open new connection
E (9492) TRANS_SSL: Failed to open a new connection
E (9502) HTTP_CLIENT: Connection failed, sock < 0
E (9502) native_ota_example: Failed to open HTTP connection: ESP_ERR_HTTP_CONNEC
T
E (9512) native_ota_example: Exiting task due to fatal error...

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What am I doing wrong?
Is there anything to do with cipher suits?
is this example only works with local server.