Mark Waite added a comment - 2021-03-18 13:51 Thanks for providing the plugins.txt file. I was able to duplicate the problem as you reported it and was able to confirm that the problem can be resolved by acting on the warnings that Jenkins displays. Jenkins warns that there are security vulnerabilities in 3 of the plugins. Jenkins warns that several of the plugins are deprecated and no longer maintained. If the plugins with security warnings and the deprecated plugins are removed, then the Freestyle project saves successfully. The analysis and violations plugins have been replaced by the warnings-ng plugin. The replacement is a significant improvement. There is no replacement for the tfs plugin and no active maintenance of that plugin. It was removed from the Jenkins update center because it requires close source components. Your options include: Remove the plugins analysis-core, pipeline-model-declarative-agent, tfs, violations, vsts-cd Experiment with removing a subset of those plugins to identify which of them is causing the issue (I assume it is either tfs plugin or vsts-cd plugin) Remain with Jenkins 2.263.4

Mikle added a comment - 2021-03-19 15:55 Thanks. I try it on test stend. For resolve i need to delete plugin fts or roolback to 2.263.4. I'll try it later on prod.