Pass SoapUI's Proxy Settings File with -t
Keep the runner settings XML separate from the project XML, and select the file under the actual headless runner account.
testrunner.bat -t "C:\Tests\soapui-settings.xml" ^
"C:\Tests\service-soapui-project.xml"This is Command Prompt syntax with testrunner.bat on the path. -t selects preferences such as proxy, SSL and HTTP settings; the final XML is the project. Use the equivalent runner and quoting on other platforms.
Prepare settings with the installed SoapUI version and intended proxy mode, endpoint and account. GUI success can depend on that user's preferences outside the project.
In CI, choose a stable path readable by the runner account. Copying a settings file into the checkout does not select it. If the loaded values change, inspect project setup scripts that modify SoapUI.settings; saving is for persistence, not necessary just to load an existing file.
Protect any account material in the file and keep a proxy login rejection distinct from SOAP service authentication or message security.