Hello. Dremel 3D45 must work fine using network/ethernet connection (without 3dprinteros client) as well as using USB via 3DPrinterOS client.
You can use "Report Problem" button in 3dprinteros client web interface (127.0.0.1:8008 in browser, when you use USB connection) to send logs with problem, so we can analyze it. But at first, is it possible that you have some other software started that can hold usb connection so our client was not able to connect?
Debugging wireless/ethernet connection is more complicated because it works directly with printers firmware, but it is still possible if you need it.