Depends on the make and model which, for some reason you decided not to tell us but generally a flashing red (or steady red) light on a freezer means it is too warm.
Has the door been left ajar for a long period?
Is the freezer plugged in? Is there electricity at the outlet? Has the thing been turned off at its control panel (some makes and models have an on/off switch but, for some reason you decided not to tell us what yours is) - actually, scratch that: you have a red light that suggests power is good.
Can you hear the compressor running?