Diagnosis
The thermoelectric cooling module (the solid-state 'engine' in the back) is probably failing. These modules lose efficiency over time and can't pump enough heat out. Alternatively, the interior temperature sensor is giving a false reading to the board.
How to Fix It
First, rule out environment. Is it in a hot garage or right next to an oven? It needs space for ventilation at the back and sides. Move it to a cooler, well-ventilated spot. Clean the rear heatsink and fan of all dust with compressed air—overheating kills performance.
If That Didn't Work
The thermoelectric module itself is likely degraded. For a unit that's several years old, this is the expected failure mode. Replacing it is a major repair involving disassembly and thermal paste, often not cost-effective.
Heads Up
These are beverage coolers, not freezers. In a warm room (above 80°F), they will struggle to hit 34°F. Expect a delta of about 20-30 degrees below ambient temperature at best when they're working perfectly.