IBM Mobile First - Http request failed: javax.net.ssl.SSLHandshakeException

Question

I am trying to consume an OData service using SAP Netweaver Gateway Adapters. But I am facing an issue like below

Runtime: Http request failed: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

Here is my worklight.properties

##########    MobileFirst SSL keystore  
#############################################
#SSL certificate keystore location.
ssl.keystore.path=conf/default.keystore
#SSL certificate keystore type (jks or PKCS12)
ssl.keystore.type=jks
#SSL certificate keystore password.
ssl.keystore.password=<keystorepassword>

Here is my adapter.xml

    <connectivity>
    <connectionPolicy xsi:type="nwgateway:NWGatewayHTTPConnectionPolicyType">
        <protocol>https</protocol>
        <domain>mydomain</domain>
        <port>myport</port>
        <connectionTimeoutInMilliseconds>30000</connectionTimeoutInMilliseconds>
        <socketTimeoutInMilliseconds>30000</socketTimeoutInMilliseconds>
        <serviceRootUrl>/sap/opu/odata/SAP/ZBIN_POC_SRV/</serviceRootUrl>
         <authentication>
            <basic/>
            <serverIdentity>
                <client>001</client>
                <username>username</username>
                <password>password</password>
            </serverIdentity>
        </authentication>   
        <!-- Following properties used by adapter's key manager for choosing specific certificate from key store-->  
        <sslCertificateAlias></sslCertificateAlias> 
        <sslCertificatePassword></sslCertificatePassword>
        <maxConcurrentConnectionsPerNode>50</maxConcurrentConnectionsPerNode>                           
    </connectionPolicy>     
</connectivity>

<procedure name="retrieveTravelAgency"/>

And also I imported default.keystore here, PFA

Here is the link I am following.

Can anyone help me out on this, Thanks in advance.