To download the latest Razer Lachesis firmware from the Razer Support site, please refer to this link –
Click on Download and save the file onto your desktop.
Once the setup.exe file is executed, you will be prompted with the following screen.
Click on Start to continue with the firmware update. There will be an indicator bar to show the progress
Once completed, you will be prompted with the following screen.
Follow the instructions accordingly before using the Razer Lachesis mouse once again.