Release is failing with ‘Object reference not set to an instance of an object’

In case your release is failing with 'Object reference not set to an instance of an object' post upgrade of your TFS with below snapshot just after creating the release

nullexecption

In case you have moved your TFS server from one machine to other and ran PrepareClone, ChangeServerID, RemapDb following command https://www.visualstudio.com/en-us/docs/setup-admin/command-line/tfsconfig-cmd

Workaround: - Create a new project in the same collection and trigger a release which should succeed. Later go back to your old project and trigger release it should work.