On our firmware downloads page, we list two versions of the SM4 firmware - one for the SM4 and SM4Bat FS, and a separate version for the SM4Bat ZC. If you install the wrong version of the firmware on your recorder, you will see an error message and be unable to access the main menu.
To solve this, load the correct version of the firmware onto an SD card and insert it into Slot A of the recorder. Then, power the recorder on while holding the UP button. This will open the prompt to install a firmware file from the SD card.