[Google Pixel XL Questions & Answers] CZ Eddie:
There does not appear to be a safe mode option for fastboot.

I'm very uncomfortable offering suggestions here because I'm out of my depth and your phone is a Verizon that was unlocked and then re-locked which is even more of an unknown for me.

Have you tried to fasboot anything like flash-all.bat or fastboot boot twrp.img just to see what happens?

I'm just throwing stuff on the wall here. TWRP probably won't work because it sounds like you're relocked.

Anything you do from here on could likely brick your phone even harder.

Here's a list of fastoot commands.

I'm really interested to know if unlock works, or if the critical unlock works and lets you boot a boot img or something to gain access to recovery.

Check out all the various unlock options.

Again, I'm out of my depth and doing ANYTHING here could brick you harder.

May be best to wait for some better help.

C:\Users\xxx\AppData\Local\Android\sdk1\platform-tools>fastboot
usage: fastboot [ <option> ] <command>

commands:
update <filename> Reflash device from update.zip.
Sets the flashed slot as active.
flashall Flash boot, system, vendor, and --
if found -- recovery. If the device
supports slots, the slot that has
been flashed to is set as active.
Secondary images may be flashed to
an inactive slot.
flash <partition> [ <filename> ] Write a file to a flash partition.
flashing lock Locks the device. Prevents flashing.
flashing unlock Unlocks the device. Allows flashing
any partition except
bootloader-related partitions.
flashing lock_critical Prevents flashing bootloader-related
partitions.
flashing unlock_critical Enables flashing bootloader-related
partitions.
flashing get_unlock_ability Queries bootloader to see if the
device is unlocked.
flashing get_unlock_bootloader_nonce Queries the bootloader to get the
unlock nonce.
flashing unlock_bootloader <request> Issue unlock bootloader using request
.
flashing lock_bootloader Locks the bootloader to prevent
bootloader version rollback.
erase <partition> Erase a flash partition.
format[:[<fs type>][:[<size>]] <partition>
Format a flash partition. Can
override the fs type and/or size
the bootloader reports.
getvar <variable> Display a bootloader variable.
set_active <slot> Sets the active slot. If slots are
not supported, this does nothing.
boot <kernel> [ <ramdisk> [ <second> ] ] Download and boot kernel.
flash:raw boot <kernel> [ <ramdisk> [ <second> ] ]
Create bootimage and flash it.
devices [-l] List all connected devices [with
device paths].
continue Continue with autoboot.
reboot [bootloader] Reboot device [into bootloader].
reboot-bootloader Reboot device into bootloader.
help Show this help message.

options:
-w Erase userdata and cache (and format
if supported by partition type).
-u Do not erase partition before
formatting.
-s <specific device> Specify a device. For USB, provide ei
ther
a serial number or path to device por
t.
For ethernet, provide an address in t
he
form <protocol>:<hostname>[:port] whe
re
<protocol> is either tcp or udp.
-p <product> Specify product name.
-c <cmdline> Override kernel commandline.
-i <vendor id> Specify a custom USB vendor id.
-b, --base <base_addr> Specify a custom kernel base
address (default: 0x10000000).
--kernel-offset Specify a custom kernel offset.
(default: 0x00008000)
--ramdisk-offset Specify a custom ramdisk offset.
(default: 0x01000000)
--tags-offset Specify a custom tags offset.
(default: 0x00000100)
-n, --page-size <page size> Specify the nand page size
(default: 2048).
-S <size>[K|M|G] Automatically sparse files greater
than 'size'. 0 to disable.
--slot <slot> Specify slot name to be used if the
device supports slots. All operations

on partitions that support slots will

be done on the slot specified.
'all' can be given to refer to all sl
ots.
'other' can be given to refer to a
non-current slot. If this flag is not

used, slotted partitions will default

to the current active slot.
-a, --set-active[=<slot>] Sets the active slot. If no slot is
provided, this will default to the va
lue
given by --slot. If slots are not
supported, this sets the current slot

to be active. This will run after all

non-reboot commands.
--skip-secondary Will not flash secondary slots when
performing a flashall or update. This

will preserve data on other slots.
--unbuffered Do not buffer input or output.
--version Display version.
-h, --help show this message.

C:\Users\xxx\AppData\Local\Android\sdk1\platform-tools>

---------- Post added at 05:39 PM ---------- Previous post was at 05:37 PM ----------

Here is my guide for the flash-all.bat if you want to see if it works.

I think you might have to be unlocked though?

https://xdaforums.com/pixel-xl/how-to/info-how-restored-to-stock-soft-t3494478