The certificate in the screenshot is not the one which we try to import. There is a mismatch in the expiry date of it. We have followed the export steps. Still, we have some options disabled. The screenshots of them are attached herewith. Thank you.
Did you also review our article for procuring a CA certificate? It has detailed instructions for the specifics required. If not, you should contact the certificate authority who provided the s/mime certificate. There's something preventing you from exporting both the private and public keys, which are required to create the Java keystore.
Jesse Wilson Solution Architect - Data Integrations Singapore