A network administrator registered a new FTD to an existing FMC. The administrator cannot place the FTD in transparent mode. Which action enables transparent mode?

Adding a Bridge Group Interface (BVI) is a step in configuring transparent mode, but it does not enable the mode itself if the FTD is already registered to an FMC.

When a Cisco FTD device is managed by a Firepower Management Center (FMC), its operational mode (routed, transparent, or passive) cannot be changed directly through the FMC GUI. To switch the FTD to transparent mode, the device must be deregistered from the FMC, the mode configured via the FTD's CLI, and then the device can be re-registered to the FMC.

Transparent mode is a fundamental feature of Cisco FTD, and it is highly unlikely that the issue is due to model incompatibility without specific context.

Assigning IP addresses to two physical interfaces is characteristic of routed mode deployment, not transparent mode which operates at Layer 2.