Here’s how to fix ADB Error – “FAILED (remote: variable not found)” if you get this error while trying to update your Android smartphone, which may likely happen on newer phones like the Pixel 2, Pixel 2XL, Pixel 3, or Pixel 3XL
Checking partition-exists… FAILED (remote: variable not found)
This is because you are using older version of fastboot. We have updated our fastboot.zip to include the latest September 2018 update for both ADB and fastboot so download the latest fastboot.zip and try again, the error will go away.