ADB/Fastboot not detecting Android stuck in bootloader

Question

I tried to flash the most recent android pie update to my pixel 2 only for it to fail writing partitions even though I followed a recent guide to my best ability. Now, the phone is stuck in the bootloader with no way to boot into android or any way to access the recovery options (throws an error and takes me back to the bootloader info page)

Neither fastboot nor ADB can recognize the phone, I think this is because the USB debugging must have turned off somehow even though I turned it on, as before I WAS able to access it through fastboot. But now I can not, plugging it into the Windows machine, windows doesn't see any change in Device Manager when the phone is plugged in and out.

I reached out to a google supports rep and they told me since there is no way to access the recovery options, the phone needs to go through warranty, but is this really the only way? Is there some driver I am missing?

Thank you.

— John Warts | Sources

Answer

Disclaimer: this is not necessarily a proper answer because it
involves indeterministic and rather sporadic approaches. That said,
thought it'd still be worth it to jot it down and share it for
informational purpose. :)

What didn't work for me:

âœ— Using my newer Mac (2019/Big Sur) whose USB ports are USB-C/3.1.

âœ— Trying out various USB 2.0 cables and adapters (USB-C/3.1 <-> USB-A/2.0, USB-A/3.0 <-> USB-A/2.0, etc.). More about that here (https://stackoverflow.com/a/58774581/2013891) and here (https://www.reddit.com/r/GooglePixel/comments/7lj50n/apparently_the_pixel_2_nonxl_doesnt_like_usb_3031/).

âœ— Installing Linux (Ubuntu) on VirtualBox, or any virtual machines in this case.

âœ— Getting RMA since I bought the phone secondhand on eBay [sic.] :D

What made it work for me:

âžœ Praying. (yup seriously, this could be the most important pre-step that I forgot to do when failing continuously before ;) )

âžœ Using my older Mac (2015/El Capitan) whose USB ports are USB-A/3.0.

âžœ Running fastboot getvar all. While it's saying < waiting for any device >, plugging-in and -out again the Pixel 2 (assumed it is booted already to FastBoot mode) until all the vars are printed out in the console. Note that this step is like a game of chance to me. Depending on your luck, you may need to do it 100 times or even 1000 times while wiggling the cable, waiting for a little, and making a sudden plug-in/out over and over again. Your mileage may vary, hence the praying step.

âžœ When the vars got printed, it means the hardware connection has been successfully established in the USB interface. Running fastboot devices will list your Pixel 2 device. From this point on, it's business as usual -- I did the ./flash-all.sh thingy from https://developers.google.com/android/images#walleye.

Having all these messes, I still strongly believe a few Google phone/tablet hardwares are buggy when they come to establishing USB connection. Now, even after I managed to bring my Pixel 2 back to life, it's still not able create a USB connection to do a wired files transfer unless I do the "game of chance" mentioned above. Well, at least I got it working and it's becoming usable again.

— Glenn Mohammad | Sources

ADB/Fastboot not detecting Android stuck in bootloader

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