SOLVED! Manually…
Open a terminal on your PC and reboot the device into fastboot mode by typing
adb reboot bootloader
or by using the hardware key combination for your device while it is powered off.
Once the device is in fastboot mode, verify your PC sees the device by typing
fastboot devices
If you don’t see your device serial number, and instead see “<waiting for device>”, fastboot is not configured properly on your machine. See fastboot documentation for more info.
If you see “no permissions fastboot”, make sure your UDEV rules are setup correctly.
Flash recovery onto your device by entering the following command:
fastboot flash recovery your_recovery_image.img
where the latter part is the filename of the recovery image.
Once the flash completes successfully, reboot the device into recovery to verify the installation.
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