as I want activate Bitlocker for the system drive (C) with an USB key on my Surface Pro, I have activated the corresponding Local Computer Policy (Computer Configuration > Administrative Templates > Windows Components > BitLocker Drive Encryption > Operating System Drives > "Require Additional Authentication at Startup") to allow this feature. After I confirmed bitlocker encryption the key file is saved to the USB drive and windows restarts for a system check.

Unfortunately as my Surface Pro reboots the following happens:

1. Startup "SURFACE" Logo appears, then
2. Black Screen / Restart, then
3. Startup "SURFACE" Logo appears again, then after some seconds
4. At the bottom of the screen it appears that the "Repairing mode" is started

The screen remains this way until the USB key is removed (sometimes I have even to restart the Surface completely in order to boot regulary).

Back in windows the error message appears that Bitlocker encrpytion failed since the encryption key cannot be read from TPM. - However, even deleteing the TPM and re-initialize it does not help.

Does anyone know what the problem is and how to activate Bitlocker system drive encryption on the Surface Pro?