If your chromebook automatically boots into the "recovery mode" (or the screen with the Yellow exclamation point) hit "tab" on your keyboard. Look next to recovery_reason in the second line of text. If you see "TPM Error in read-only firmware", you will need to apply the fix below.
The TPM fix:
You may need to repeat steps (1-3) approx. 20-25 times to clear the TPM error but it usually works within 6-10 attempts.
Power on the Chromebook and leave it on for approx. 30 sec
Then turn it off by holding the "power" button down for approx. 7 seconds
When the Chromebook is off, wait a couple seconds and push the power button once to turn back on