Processing 4.3 cannot read GPIO on Raspberry Pi 400

Processing for Pi
1

I’m trying to run the SimpleInput sketch and am getting this error:

GPIO pin 4 does not seem to be available on your platform
RuntimeException: /sys/class/gpio/export: Invalid argument
RuntimeException: /sys/class/gpio/export: Invalid argument

accessing the same pin from a basic gpiozero program works fine, so it’s not an issue with the wiring

my system is fully up to date. Any clue what might be causing this?