MacBook Pro M1 14’ not booting after I began erase drive in utility and had a thumb drive with Sequoia for it (I was on the Tahoe version that is new but no thumb drive for that) . Since then my thumb drive now says it’s not formatted for GUI (I did have it set for GUI and have used it once) but now all it will go to (including trying online) is “OPTIONS” and the wheel keeps spinning.
iPhone 13, iOS 26
I've never tried booting from a USB drive & erasing the internal SSD of an M-series Mac, then trying to boot from the external again. With the 2018+ Macs with the secure enclave chip, you may not be able to boot from an external drive if there are no valid macOS user accounts on the internal SSD with which to authenticate (security feature). I don't know if this is the case here with an M1 Mac.
And how & what did you erase on the internal SSD? You have to be a lot more careful about what you erase on the internal SSD of the M-series Macs when using Disk Utility. At best you should only erase the Volume Group.
If you cannot reinstall macOS using Recovery Mode as suggested by @D.I. Johnson, then you will need to perform a DFU Firmware Restore which resets the security enclave chip, system firmware, and internal SSD & pushes a clean copy of macOS onto the internal SSD (not sure what version of macOS, but at least you can start the downgrading process over again if needed). Unfortunately this option requires access to another Mac currently running macOS 26.x Tahoe, or macOS 15.7.3+ Sequoia.
It is not clear whether your thumb drive is a bootable macOS Sequoia USB installer, or just if it is just a full macOS Sequoia installation. I'm guessing installer since it is a thumb drive, but I've learned never to make such assumptions on this forum If it is a bootable macOS Sequoia USB installer, then did you use the instructions in the following Apple article to create it?
Create a bootable installer for macOS - Apple Support
FYI, a bootable macOS USB drive (installer or full macOS installation) needs to have a GUID partition type. The installer will have a MacOS Extended (Journaled) file system, while a full blown macOS installation will use the APFS file system (for macOS 10.13+).
If the USB stick was using a GUID partition and now it doesn't have it, then either this USB stick was erased, or it is defective.
Make sure to disconnect the USB stick and any other connected devices as they may be causing the spinning wheel on your Startup Options screen. If you get the spinning wheel with nothing connected & it is not trying to connect to the network, then you will probably need to resort to a DFU Firmware Restore. There is also a possibility the laptop has a hardware issue as well since you did not mention why you are reinstalling macOS here. That same reason may be why you are having issues here.
I've never tried booting from a USB drive & erasing the internal SSD of an M-series Mac, then trying to boot from the external again. With the 2018+ Macs with the secure enclave chip, you may not be able to boot from an external drive if there are no valid macOS user accounts on the internal SSD with which to authenticate (security feature). I don't know if this is the case here with an M1 Mac.
And how & what did you erase on the internal SSD? You have to be a lot more careful about what you erase on the internal SSD of the M-series Macs when using Disk Utility. At best you should only erase the Volume Group.
If you cannot reinstall macOS using Recovery Mode as suggested by @D.I. Johnson, then you will need to perform a DFU Firmware Restore which resets the security enclave chip, system firmware, and internal SSD & pushes a clean copy of macOS onto the internal SSD (not sure what version of macOS, but at least you can start the downgrading process over again if needed). Unfortunately this option requires access to another Mac currently running macOS 26.x Tahoe, or macOS 15.7.3+ Sequoia.
It is not clear whether your thumb drive is a bootable macOS Sequoia USB installer, or just if it is just a full macOS Sequoia installation. I'm guessing installer since it is a thumb drive, but I've learned never to make such assumptions on this forum If it is a bootable macOS Sequoia USB installer, then did you use the instructions in the following Apple article to create it?
Create a bootable installer for macOS - Apple Support
FYI, a bootable macOS USB drive (installer or full macOS installation) needs to have a GUID partition type. The installer will have a MacOS Extended (Journaled) file system, while a full blown macOS installation will use the APFS file system (for macOS 10.13+).
If the USB stick was using a GUID partition and now it doesn't have it, then either this USB stick was erased, or it is defective.
Make sure to disconnect the USB stick and any other connected devices as they may be causing the spinning wheel on your Startup Options screen. If you get the spinning wheel with nothing connected & it is not trying to connect to the network, then you will probably need to resort to a DFU Firmware Restore. There is also a possibility the laptop has a hardware issue as well since you did not mention why you are reinstalling macOS here. That same reason may be why you are having issues here.
If I understand you correctly, you are trying to downgrade your Mac from Tahoe to Sequoia, but the bootable thumb drive is no longer recognized as a valid startup device.
From the point you are at you'll have to reinstall macOS from Recovery, using whatever macOS version is offered.
Downgrading is no small task and never to be taken lightly.
MacBook Pro M1 not booting, stuck on 'Options' screen
