Since upgrading to the Artifactory plugin version 3.16.0 the default credentials we have configured for out Artifactory server no longer appear in the dropdown. The last working version we used before this was 3.13.2. The workaround were having to use is as follows:
1. Go into "Configure System"
2. Go to the JFrog settings section
3. Uncheck "Use the Credentials Plugin"
4. Enter our username and password under "Default Deployer Credentials"