I had the same problem. What ended up happening is that I borked the bootloader on the M8P, and the CM4 could not see the M8P board when I ran the lsusb command. What I ended up doing was flashing the bootloader available in the Manta-M8P/V2.0 repo (link) with dfu-util.
- Press and hold the boot0 button of M8P first, then (while holding boot0) click the reset button to make the M8P boot into DFU mode.
- You can confirm that the M8P is in DFU mode by running lsusb. The device should show up as 'STMicroelectronics STM Device in DFU Mode'
- After running lsusb and confirm that the device is in DFU mode, copy the ID. For my M8P, it was "0483:df11"
- While logged in to the CB1/CM4, follow these steps to download and write the bootloader (M8P_V2_H723_bootloader.bin) to the chip:
If you haven't downloaded the bootloader yet, download it first: