Hello. I am sorry you are having trouble getting the Maestro to work on your Mac.
It sounds like you used the “Add Legacy Hardware” option in the Device Manager in an attempt to get the Maestro to work. This option is only for older devices that do not support Plug and Play and I do not expect it to help.
I recommend unplugging the Maestro from your computer. After you do that, please look for any entries in the Device Manager that have Maestro in the name. These entries do not correspond to an actual Maestro, and are just non-working entries that you added using the “Add Legacy Hardware” option. To avoid any issues that these entries might cause, please right-click each entry, select “Uninstall”, and then click “OK”. Do not check the box asking you if you want to delete the driver software for the device.
Next, please plug the Maestro in to your computer via USB. Do you see any entries for the Maestro in the Device Manager? Be sure to check the “Pololu USB Devices”, “Ports (COM & LPT)”, and “Other devices” categories. What are the three LEDs on the Maestro doing?
–David