AO-100 connection issues

My AO-100 has recently stopped connecting to my computer. When I try to connect to Cura it says “Connection Closed” after a little delay. So I tried using pronterface which says

[ERROR] Could not connect to COM3 at baudrate 115200:
Serial error: could not open port COM3: [Error 170] The requested resource is in use.

I’ve tried disabling and enabling the COM3 port in the device manager, but that has no effect.

Also, the printer works with another computer, but not with mine. Any suggestions on where to go from here?

It sounds like you could be missing the RAMBo drivers on that computer in order to connect. You can manually install the drivers by following these directions: or you can install Cura LulzBot Edition and the drivers will automatically be installed in that process:

If you are still having problems, feel free to reach out to our support team at