Thanks for the log file. The line at the end of the message suggests that the KNIME Executor Connector extension is not installed.
You may choose to download a full build which includes the extension which is available from the product downloads page. In that case uncompress the download to a location of your choice and then update the /opt/knime_server/workflow_repository/config/knime-server.config to point to the newly downloaded KNIME executable.
or alternatively you can use the following terminal command to install the extension.
/opt/knime_server/knime_executor/./knime -application org.eclipse.equinox.p2.director -nosplash -consolelog -r https://update.knime.com/analytics-platform/3.5,https://update.knime.com/store/3.5
-i com.knime.features.enterprise.slave.feature.group -d /opt/knime_server/knime_executor/
java.lang.RuntimeException: Application “com.knime.enterprise.slave.KNIME_REMOTE_APPLICATION” could not be found in the registry. The applications available are: com.knime.enterprise.client.filesystem.KNIME_WORKFLOW_DOWNLOADER, com.knime.enterprise.client.filesystem.KNIME_WORKFLOW_UPLOADER, org.eclipse.ant.core.antRunner, org.eclipse.birt.report.engine.ReportExecutor, org.eclipse.e4.ui.workbench.swt.E4Application, org.eclipse.e4.ui.workbench.swt.GenTopic, org.eclipse.equinox.app.error, org.eclipse.equinox.p2.director, org.eclipse.equinox.p2.garbagecollector.application, org.eclipse.equinox.p2.publisher.InstallPublisher, org.eclipse.equinox.p2.publisher.EclipseGenerator, org.eclipse.equinox.p2.publisher.ProductPublisher, org.eclipse.equinox.p2.publisher.FeaturesAndBundlesPublisher, org.eclipse.equinox.p2.reconciler.application, org.eclipse.equinox.p2.repository.repo2runnable, org.eclipse.equinox.p2.repository.metadataverifier, org.eclipse.equinox.p2.artifact.repository.mirrorApplication, org.eclipse.equinox.p2.metadata.repository.mirrorApplication, org.eclipse.equinox.p2.touchpoint.natives.nativePackageExtractor, org.eclipse.equinox.p2.updatesite.UpdateSitePublisher, org.eclipse.equinox.p2.publisher.UpdateSitePublisher, org.eclipse.equinox.p2.publisher.CategoryPublisher, org.eclipse.help.base.infocenterApplication, org.eclipse.help.base.helpApplication, org.eclipse.help.base.indexTool, org.eclipse.jdt.core.JavaCodeFormatter, org.eclipse.jdt.core.JavaIndexer, org.eclipse.ui.ide.workbench, org.knime.product.KNIME_APPLICATION, org.knime.product.KNIME_BATCH_APPLICATION, org.knime.product.KNIME_PROTOCOL_APPLICATION, org.knime.workbench.help.KNIME_Documentation_Builder, org.knime.workbench.repository.NodeDocumentationGenerator.