That error is from the RTL driver (rtlsdr.dll and libusb-1.0.dll)
You will probably need to shutdown DSD+ and FMP24 and pull the dongles from the USB ports. (Maybe even restart PC)
Plug in dongles again and restart FMP24/DSD+.
More info:
In testing I have done in the past, the -9 (LIBUSB_ERROR_PIPE) value is returned to the RTL driver from the libusb call to 'libusb_control_transfer'