Same as with the latest Monitoring Service plugin update, something went wrong with the build and REST API is not showing its admin pages. User also report it doesn't authenticate correctly.
Plugin should be reverted to 1.3.1 on Downloads until this is fixed.
As with the monitoring service, the restAPI is currently being built with a parent of Openfire 4.3.0-SNAPSHOT. I suspect that dropping it to 4.2.0 should make it compatible with Openfire 4.2.
should no longer be an issue, 1.3.5 is on the website now