Hi Holger,
there is a discussion going on about LightBurn 1.0.00 having issues with Mac and USB connections that is currently been investigated by the developers. You can follow this discussion here:
However, if this would be the case in your scenario all should be fine again if you go back to LightBurn Version 0.9.24 (which can still be downloaded here) or if you connect your Mac via an Ethernet Cable to the Ruida DSP.
Good luck and cheers,
Brian