Delete old serial config

[jim321]

see if you can find out anything with these commands

ls /dev/tty*

grep tty

you could also try to power down and remove the hat power on and see if its still there.
someone else with a hat might know ?

also check.
sudo nano /boot/config.txt if there's a line "enable_uart=0" remove or comment it out #
ctrl x y enter
reboot