So. If you should find that the code runs from the debugger, but does not start on its own when you plug in the usb, add to your rootmost CMakeLists.txt

set(PICO_BOARD pico_pair)

but add these three lines near the top, after the name definition (maybe rename the name lines appropriately)

#ifndef PICO_XOSC_STARTUP_DELAY_MULTIPLIER

#define PICO_XOSC_STARTUP_DELAY_MULTIPLIER 64

#endif

See, for instance, https://forum.micropython.org/viewtopic.php?t=12695