While launching the robot tray in 20.4.1 robot version user gets error "Communication with the Robot Service fails. Please try to restart the service.".
While browsing the UiPath Assistant we may get "Communication with the Robot Service fails. Please try to restart the service." error in 20.4.1 robot version.
This is due to the UIPATH_USER_SERVICE_PATH variable gets auto created in the environment variable under both user variable & System variable.
Delete UIPATH_USER_SERVICE_PATH variables from both user variable under environment variable window and launch the robot tray again will resolve the issue.
Also, verify we should not have two different version of UiPath Studio/Robot installed in the machine, as it also causes the similar issues.