These are the conditions for HOLD to function
Activation conditions
You can activate the HOLD function if:
The vehicle is stationary
The engine is running or if it has been automatically switched off by the ECO start/ stop function
The driver's door is closed or your seat belt is fastened
The hood is closed
The electric parking brake is released
The selector lever is in position D, R or N on vehicles with automatic transmission
DISTRONIC PLUS is deactivated