I am having the exact same problem and have followed the exact same steps except I used Python Zeep instead of curl where it worked. I also have a .pfx file and while I was able to successfully add that to the keystore, I could never successfully make the connection as I have a feeling the service wants a separate .crt and .key file.
So I was able to finally connect. I don't know if this applies to you, but after adding the certificate to the KeyStore, I added the certificate to the `SSL Keystore` property as indicated in the screenshot where I have the cert blacked out and it worked.
