Hi. You can download the CH340 driver from here: CH340 Driver
But Win10 should find this automatically.
You can find the documentation for RAK WisNode Button 4K(RAK7201) here.
Similar issue with trying to connect Serial Tool to a 7204. I get the connection tone when plugging 7204 into USB but 4 COM ports display in the tool when I only have one, and none of them will open the Port. Worked fine previously (pre Windows update). Disconnecting 7204 does not change available ports. Downloaded Serial Tool again but no difference. Tried a different cord, pushed reset, reconnected battery. No change.