The above error is displayed, install the plug cloudbees-folder failed because there are no download Jenkins.war cloudbees-folder plug-ins
Https://updates.jenkins-ci.org/download/plugins/cloudbees-folder/ need to download a plug-in
Download cloudbees-folder.hpi in the tomcat / webapps / jenkins / WEB-INF / detached-plugins / can be.
Then restart tomcat.