Distributed Rendering stopped working after the installation of newer version

There are two usual causes:

1. Corona License is not activated
Solution: Activate your Corona License on master PC and each render slave

2. The version of DrServer is different than the version of Corona Renderer installed on your system. Please check if the title of the DrServer window corresponds to your version of Corona Renderer (for example DrServer | 1.00.01). If it is different, then use the Universal Installer and re-install the new version of DrServer.
Link: Universal Installer