javax.net.ssl.SSLHandshakeException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
  at java.base/sun.security.ssl.Alert.createSSLException(Unknown Source)
  at java.base/sun.security.ssl.TransportContext.fatal(Unknown Source)
  at java.base/sun.security.ssl.TransportContext.fatal(Unknown Source)
  at java.base/sun.security.ssl.TransportContext.fatal(Unknown Source)
  at java.base/sun.security.ssl.CertificateMessage$T13CertificateConsumer.checkServerCerts(Unknown Source)
  at java.base/sun.security.ssl.CertificateMessage$T13CertificateConsumer.onConsumeCertificate(Unknown Source)
  at java.base/sun.security.ssl.CertificateMessage$T13CertificateConsumer.consume(Unknown Source)
  at java.base/sun.security.ssl.SSLHandshake.consume(Unknown Source)
  at java.base/sun.security.ssl.HandshakeContext.dispatch(Unknown Source)
  at java.base/sun.security.ssl.HandshakeContext.dispatch(Unknown Source)
  at java.base/sun.security.ssl.TransportContext.dispatch(Unknown Source)
  at java.base/sun.security.ssl.SSLTransport.decode(Unknown Source)
  at java.base/sun.security.ssl.SSLSocketImpl.decode(Unknown Source)
  at java.base/sun.security.ssl.SSLSocketImpl.readHandshakeRecord(Unknown Source)
  at java.base/sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
  at java.base/sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
  at java.base/sun.net.www.protocol.https.HttpsClient.afterConnect(Unknown Source)
  at java.base/sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(Unknown Source)
  at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown Source)
  at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
  at java.base/sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(Unknown Source)
  at org.jabref@5.1.60000/org.jabref.logic.util.Version.getAllAvailableVersions(Unknown Source)
  at org.jabref@5.1.60000/org.jabref.gui.help.VersionWorker.getNewVersion(Unknown Source)
  at org.jabref@5.1.60000/org.jabref.gui.util.BackgroundTask$1.call(Unknown Source)
  at org.jabref@5.1.60000/org.jabref.gui.util.DefaultTaskExecutor$1.call(Unknown Source)
  at org.jabref.merged.module@5.1.60000/javafx.concurrent.Task$TaskCallable.call(Unknown Source)
  at java.base/java.util.concurrent.FutureTask.run(Unknown Source)
  at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
  at java.base/java.util.concurrent.FutureTask.run(Unknown Source)
  at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
  at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
  at java.base/java.lang.Thread.run(Unknown Source)
Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
  at java.base/sun.security.validator.PKIXValidator.doBuild(Unknown Source)
  at java.base/sun.security.validator.PKIXValidator.engineValidate(Unknown Source)
  at java.base/sun.security.validator.Validator.validate(Unknown Source)
  at java.base/sun.security.ssl.X509TrustManagerImpl.checkTrusted(Unknown Source)
  at java.base/sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(Unknown Source)
  ... 28 more
Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
  at java.base/sun.security.provider.certpath.SunCertPathBuilder.build(Unknown Source)
  at java.base/sun.security.provider.certpath.SunCertPathBuilder.engineBuild(Unknown Source)
  at java.base/java.security.cert.CertPathBuilder.build(Unknown Source)
  ... 33 more