DIAGNOSIS The compressor is likely running, but the refrigerant isn't circulating. The most common culprit is the unit being too close to a wall or in a cabinet, blocking the rear condenser coils from getting enough air to dump the heat.
FIX First, power it off and unplug it. You need to give the back of the fridge a good 6-8 inches of clearance, especially at the top and bottom where the vents are. Pull it out, make sure those black coil fins aren't caked with dust or pet hair—a vacuum with a brush attachment works great. Let it sit unplugged for about 10 minutes, then plug it back in and set it to a cold temp, like 38°F. Give it a full 24 hours to stabilize before checking the temp inside with a separate thermometer.
IF THAT DIDN'T WORK If there's still no cooling after a day with proper clearance, the issue might be a failed start component on the compressor or a refrigerant leak. Since it's a sealed system, this isn't a DIY fix. You'll need to contact Manastin support for warranty service or a local appliance repair tech.
HEADS UP These coolers work a lot harder in a warm garage or basement. If the room temp is above 80°F, it might struggle to hit a very low setting. It's designed for indoor, climate-controlled spaces.