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There are two reasons because of which your application is not working. First, the certificates in the resources/azure_iot_hub which are accessed by the application expired on 30th sept 2017. The certificates are renewed in 6.0 and so you shouldn't see the problem now. In the log you have provided, the certificate doesn't seem to be the issue as they are valid until December.
Secondly, you are getting an error in state 7: Write MBEDTLS_SSL_CLIENT_CERTIFICATE. You need to add the code to access client certificate and privkey certificate.