You want to know why you are getting the "Unable to Encrypt" status in WFBS-SVC 6.1 for UEFI-based firmware computers.
WFBS-SVC 6.1 leverages Microsoft's Bitlocker encryption to encrypt devices. However, the current WFBS-SVC version does not support the Encrypt command on UEFI-based firmware computers. As a workaround, you may encrypt the drive directly on the device using Bitlocker.
The Encrypt command on UEFI-based firmware computers will be supported in WFBS-SVC 6.2, which is scheduled to be released on Q3 this year.