I've been trying to get the GitHub Pull Request Builder plugin working.

I set it up based on the instructions listed on the plugin page.

After creating a new pull request, I can confirm Jenkins receives the payload in the logs:

Mar 12, 2014 10:32:33 AM INFO org.jenkinsci.plugins.ghprb.GhprbRootAction doIndex
Got payload event: pull_request

Unfortunately, it stops there. No build gets triggered. I did find that configuring the Jenkins job, and then saving (with no changes) will trigger the builds to start happening.

I've checked the logs to see what is happening but it only shows this from the save configure trigger.

Mar 12, 2014 10:35:54 AM INFO org.jenkinsci.plugins.ghprb.GhprbPullRequest
Created pull request #170 on test/test by <user> updated at: 3/12/14 10:18 AM SHA: <hash>
Mar 12, 2014 10:35:54 AM INFO org.jenkinsci.plugins.ghprb.GhprbRepository createCommitStatus
Setting status of <hash> to PENDING with url null and message: Merged build triggered.
Mar 12, 2014 10:35:54 AM INFO org.jenkinsci.plugins.ghprb.GhprbRepository createCommitStatus
Setting status of <hash> to PENDING with url http://<jenkinsurl>:8080/job/BuildTests/8/ and message: Merged build started.
Mar 12, 2014 10:35:54 AM INFO org.jenkinsci.plugins.ghprb.GhprbPullRequest build
Merged build triggered.
Mar 12, 2014 10:36:12 AM INFO hudson.model.Run execute
iOS SDK PR Tests #8 main build action completed: SUCCESS
Mar 12, 2014 10:36:12 AM INFO org.jenkinsci.plugins.ghprb.GhprbRepository createCommitStatus
Setting status of <hash> to SUCCESS with url http://<jenkinsurl>:8080/job/BuildTests/8/ and message: Merged build finished.