A refrigerator that stops cooling is urgent, because food can spoil within hours. Start with the basics.
Power and settings
Check that the plug is in and the socket works. Make sure the temperature setting has not been turned down by accident.
Ventilation
A fridge needs space around it to release heat. If it is pushed tightly against a wall or surrounded by items, it may struggle to cool.
Door seals
A worn or dirty door seal lets warm air in. Clean the seal and check that the door closes fully.
Frost build-up
In frost-free models, heavy frost on the back wall can point to a defrost system fault.
Protect your food
Move perishables to another fridge or a cooler with ice, and avoid opening the door more than necessary.
If the fridge still does not cool, the thermostat, fan or compressor may be at fault. Book a refrigerator technician for a diagnosis at home.