Power management. macOS tries to "sleep" the USB port to save power. Fix:
If the device is detected as a "CD" or mass storage instead of a network card, it may require a "mode-switch" which is not natively supported on macOS. Driver rd9700 macOS Monterey - Apple Support Community sr9700 usb-lan mac driver
Download and run the RD9700 Mac OS Driver.pkg file. Power management