I apologize for being late with our reply and we are sorry that you faced this issue. From the log file provided we cannot figure out what went wrong, as there are many checks carried out by Diffblue Cover in the background. At this point, since in the meanwhile we released a few more versions, we kindly ask you to update the plugin from inside the IntelliJ IDE. To do so, please select the Plugins sub-menu from the File menu and find our plugin. If it is not at the most recent version a button will allow you to update it. After this operation, restart IntelliJ and try to write unit tests for a method or a class. If you encounter any issue, please let us have the latest log file. This will be placed in %TEMP%\diffblue\log.
Kind Regards and thank you for your interest in using Diffblue Cover.
Cristian