Hi Abhi,
First, try to make sure you are able to access that HTTPS endpoint from a different tool running on the same machine where the Workstation is running - you can try web browser, your 7.5.1 Workstation, SoapUI, a REST client...
If the request works fine from a different tool, please add the following property to the Workstation.vmoptions file (you will find the vmoptions file under $DEVTEST_HOME/bin folder):
-Djavax.net.debug=ssl
This property will add debug SSL handshake information to the Workstation log files. From these debug messages we should be able to find more details about the exception you are facing.
If your request doesn't work fine from a different tool running on the same host, then the issue is not with DevTest.
In case the issue is only with DevTest, please open a support ticket and attach the workstation log files with the SSL debug details.
You can open a support case via support.ca.com or you can call the number 1-800-225-5224.
Thank you,
Heloisa