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Hey Daniil,
There's no firmware for the SR2 because none have been needed to address problems on the hardware.
The issue with the device not appearing may be that the drivers were not properly allowed through the macOS security during installation; please follow the steps in this guide from page 5 to uninstall, then start at the beginning and reinstall the drivers, making sure to open the Security & Privacy section of the System Preferences to allow the driver through the security block.