Cannot command Longmill

Although I bought my Longmill over a year ago, it wasn’t until the last couple of weeks that I started using it. I had everything connected to my mac laptop and was using UGS to load and execute GCode just fine, but today it suddenly stopped working. UGS can only see the usbmodem port intermittently. When it does, I connect but all the buttons to command it (e.g. jog, reset zero) are disabled. I checked my Mac system report under USB and it doesn’t list the longmill (I’m assuming it is supposed to). It doesn’t seem to be able to connect via CNCjs either. Green light on the arduino is on. I checked the arduino connection to the main board and that looks OK too. I’m using the USB cable that came with the Longmill and I don’t see any damage to it and the connection isn’t loose.

Does anyone have any ideas on how I might troubleshoot the problem?

I’m considering buying a replacement Arduino from Sienci, but wanted to check here first. If I do buy a replacement, does it come with the proper firmware preinstalled?

Thanks in advance for your help. -Steve