Hi,
You can find some information about the plugin configuration from here:
https://github.com/zeroturnaround/gradle-jrebel-plugin
Did you add the mavenCentral repository and the necessary dependencies to the build.gradle?
If everything seems to be working ok, would it be possible for you to send us your build.gradle file so we could check if everything is set up correctly? Send it to support@zeroturnaround.com
All the best!