macOS 10.13/10.14/10.15/11.4 has implemented an additional security layer for kernel extension drivers, such as the Line 6 audio drivers. After the Line 6 device is connected, the customer must open the Security Control Pane and accept the Line 6 driver in order for the device to be recognized.
Typically, but not always you'll see this message when your driver gets blocked, or is not available for use with your DAW:
However, sometimes the driver gets blocked