Visit:
https://account.microsoft.com/devices/recoverykey
Sign in with the same Microsoft account used on the device.
You will see a 48-digit recovery key. Enter it on the blue screen.
Find your BitLocker recovery key
Unfortunately, BitLocker encryption cannot be bypassed. Your options are:
Reset the device (data will be erased)
Reinstall Windows using a Surface recovery image
Download the recovery image here from Microsoft for Microsoft Surface Pro 8: