If you have not already done so, you need to configure ssl-inspect-ca which is used for ssl forward proxy and for detecting malware in HTTPs. Shown below is just one example for configuring ssl forward proxy. For complete information, see Configuring SSL Proxy.
user@host > request security pki generate-key-pair certificate-id certificate-id size size type type
For example:
user@host > request security pki generate-key-pair certificate-id
ssl-inspect-ca size 2048 type rsa
user@host > request security pki local-certificate generate-self-signed
certificate-id certificate-id domain-name domain-name subject subject email email-id
For example:
user@host > request security pki local-certificate generate-self-signed
certificate-id ssl-inspect-ca domain-name www.juniper.net
subject "CN=www.juniper.net,OU=IT,O=Juniper Networks,L=Sunnyvale,ST=CA,C=US"
email security-admin@juniper.net
Once done, you can configure the SSL forward proxy to inspect HTTPs traffic. For example:
user@host# set services ssl proxy profile ssl-inspect-profile root-ca ssl-inspect-ca
user@host# set security policies from-zone trust to-zone untrust policy firewall-policy1 then permit application-services ssl-proxy profile-name ssl-inspect-profile
For a more complete example, see Example: Configuring a Juniper Advanced Threat Prevention Cloud Policy Using the CLI.