I have had problems with talking to the Xiao with Windows 7 on two machines both using IDE version 1.8.13. Both exhibited the same issue and the same solution worked.
On plugging the Xiao into a USB port it would appear in Device Manager under Other Devices rather than under COM Ports. To me it suggested that the correct USB driver was not available. Trying the FTDI one as recommended did not seem to work.
My solution (by experimentation) …
Right click on the wrongly placed entry in Other Devices and right click to select update driver.
Follow the following screen prompts : -
“Browse my computer for driver software”
“Let me pick from a list of device drivers on my computer”
(You might get a list of driver types so slide down to and select Com Ports)
“Select driver you want to install on this hardware”
Select Arduino LLC in the Manufacturer window
Select SmartEverything Fox bootloader and Enter (this is at the bottom of the listing)
Click to agree that you accept this regardless that it might be wrong etc
Device manager should now have moved the Xiao into Com Ports from Other Devices
Note the Com Port number that has been allocated.
Open the Arduino IDE and make sure the Xiao is showing and that it has the new Com Port allocated.
Go to “Get Board info” and you should get a small window response back suggesting it is now talking to the board OK.
Load a program such as Blink which should run and edited versions should also load.
Note on one of my machines I get an error message but it still seems to have loaded OK.
I have no idea why this works but SmartEverything appealed to me as a good driver name to try …
Alan