Maschine + Storage Mode not working

Did you find the add/remove disk/ place in settings when in standalone? It helped me once (but with a thumb drive) I pulled it out without doing it the correct way. It still was in the list of storage devices. Had to insert stick, reboot, then choose remove stick and physically remove it, reboot, and then choose add again, insert the thumb drive, followed by a full rescan. Then it worked again. Also very important make sure the software and standalone version were the ones that came out together, so 1.4.4 for standalone, 2.16 for software otherwise you can get read/write problems. And maybe far fetched but since it took such a while to show up and then break connection, are you sure you used the included usb cable and same port? Try another port (directly to the pc/Mac no hub) befor trying all the other stuff i wrote. Good luck.