How do I stop the alarm on a built-in Diplomat freezer?

Just moved house & now have built in Diplomat freezer with no manual (c. 4 yrs. old I think). I assume the kitchen was an MFI fit. The alarm sounded when first set up after 2 months 'off' so pressed the left hand button (fast freeze?) for couple hours. Now it keeps going off with the red flashing light but don't know why. Pressing in the left-hand button for a few hours is the only way to stop it but, what does it mean?