The bootloader which causes the drive to show up as a USB device is hard-wired into the RP2040 chip, so unless you’ve properly fried the chip somehow it should always work. Just to be clear, you’re holding the BOOT switch down while you power cycle the board, right? You shouldn’t release the BOOT button until after you’ve released the power button.
So I am connecting the pico via a cable to my MAC.
Make sure the power LED is Off.
Hold BOOT, press power on and then release Boot when the power led is ON.