Here is the stack trace:
Error 503 on http://********/api/system/status
java.lang.IllegalStateException: Error 503 on http://********/api/system/status
at org.sonarsource.sonarlint.core.container.connected.SonarLintWsClient.handleError(SonarLintWsClient.java:121)
at org.sonarsource.sonarlint.core.container.connected.validate.ServerVersionAndStatusChecker.fetchServerInfos(ServerVersionAndStatusChecker.java:101)
at org.sonarsource.sonarlint.core.container.connected.validate.ServerVersionAndStatusChecker.checkVersionAndStatus(ServerVersionAndStatusChecker.java:60)
at org.sonarsource.sonarlint.core.container.connected.validate.ServerVersionAndStatusChecker.checkVersionAndStatus(ServerVersionAndStatusChecker.java:50)
at org.sonarsource.sonarlint.core.WsHelperImpl.validateConnection(WsHelperImpl.java:48)
at org.sonarsource.sonarlint.core.WsHelperImpl.validateConnection(WsHelperImpl.java:43)
at org.sonarlint.eclipse.core.internal.server.Server.testConnection(Server.java:225)
at org.sonarlint.eclipse.ui.internal.server.wizard.ServerConnectionTestJob.run(ServerConnectionTestJob.java:44)
at org.eclipse.jface.operation.ModalContext$ModalContextThread.run(ModalContext.java:119)