There are several issues related to providing the TFS/Team Services Team Project Collection info for the Trigger release in TFS/Team Services post-build action.

1.) First,this action requires that the Team Project Collection connection\creds be specified within the action itself.  Yet another action (called the Set build completion status in TFS/Team Services) requires that the Team Project Collection connection\creds be specified under Jenkins->Manage Jenkins->Configure System.  It seems odd that the connection info needs to be added in two different places like this in order to use these actions. Here's a screenshot of the Team Project Collection settings found under Jenkins' Configure System settings:

2.) The Trigger release in TFS/Team Services action doesn't validate the connection at configuration time.  Right now, you have to wait until running the job and check to see whether it passed\failed.  Notice in the above screenshot that the Configuration System settings do validate the connection.

3.) The Trigger release in TFS/Team Services action doesn't use Jenkins credentials - it has the user enter in the creds directly into the action.  Instead, Jenkins global creds should be used here similar to what is shown in the Configuration System settings screenshot.