on the M5Atom there are no predefined pins assigned to RX2 and TX2. GPIO21 and GPIO25 are assigned to I2C so I would not use those. I have successfully tried GPIO19 for RX2 and GPIO22 for TX2.
Have you tried the "Cold boot" method i posted in the forum?
windows has a preinstalled driver that breaks the current driver requiring a very specific method to remove and install.
