Selecting credentials for the "Default Deployer Credentials" is broken in the artifactory plugin 3.2.3 and 3.2.4.  I've confirmed rolling back to artifactory 3.2.2 resolves the issue

To Reproduce:

1. Goto Jenkins "Configure System" page
2. Find Artifactory Settings
3. Select "Use the Credentials Plugin"
4. Attempt to add or select credentials

At this point you'll find that you cannot select existing credentials from the drop down, and adding new credentials will also not work.

Further more, any existing jobs depending on this will fail with an error..
unknown: Authentication is required

Work Around

Rollback to artifactory 3.2.2 https://updates.jenkins-ci.org/download/plugins/artifactory/