This can be done from the app/Web-frontend or by manually turning the power on and off.
From the app/Web-frontend:
Go to Settings → More → free@home settings → Service → Restart.
Manually:
If the System Access Point is installed with external power supply: unplug and replug the power cord.
If the System Access Point is installed with 230V or bus power, turn the corresponding circuit breaker on and off.