I tried opening a file from a URL on a site that uses a self-signed certificate. <oXygen/> first asked whether I wanted to allow and trust the site, and when I told it that I did, <oXygen/> refused to load it, telling me that: Cannot open the specified file. There was a problem establishing the secure HTTPS connection. In case the server you are trying to connect to uses self-signed certificates, read the 'Troubleshooting HTTPS' section from the user manual. Full error message: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target I'm running XML Editor 21.1, build 2019120214, with the bundled Java, on MacOS Mojave. How do I communicate to <oXygen/> that it should trust this site? I tried adding an exception for the site to my Java configuration, which didn't help, and I then realized that that was probably because those exceptions are for my system Java, and <oXygen/> is using its own. The instructions at Troubleshooting HTTPS<https://www.oxygenxml.com/doc/versions/21.1/ug-author/topics/import-https-server-certificate.html> in the user manual seem straightforward – where did you have problems following them? Lee