On Mac OS

1. Open System Preferences > Security & Privacy.
2. On the General section, if Blackmagic is being blocked, you will be prompted to Allow.  Unlock and Allow the Black Magic software.
   
   
3. Close and Relaunch the Blackmagic Desktop Setup and select the correct Input (SDI or HDMI).

On Windows

1. Open the Thunderbolt Control Center.
2. Confirm the Device Is Listed, and change the setting from Do Not Connect to Always Connect, then click OK.
   • You may have to go to the Approve Devices area to change this setting.