DIAGNOSIS The three-beep error is a safety interlock failure. The basket isn't seated correctly in the unit.
FIX Remove the basket. Wipe the metal sensor contacts on the front of the basket and inside the fryer cavity. Push the basket straight in until you feel a firm click. The display will show the cooking time, not just the temperature.
IF THAT DIDN'T WORK Check for food debris or grease pooled in the bottom of the fryer cavity, under the heating element. This can short the sensor. Unplug, let cool, and wipe thoroughly with a dry cloth.
HEADS UP Never force the basket. If the latch mechanism feels broken, contact Cosori support. Using it with a faulty latch is a fire hazard.