Diagnosis
A complete, silent shutdown points to a loss of power, not a grill error. The prime suspect for the portable Tailgater is the power source, especially if you're using an extension cord or a portable power generator.
How to Fix It
Eliminate the extension cord first. Plug the grill directly into a known-good, grounded household outlet. If it runs fine, the issue was your cord. Pellet grills draw a significant amount of current, especially on startup. You need a heavy-duty, 14-gauge (or thicker) extension cord that's as short as possible. A cheap, long, thin cord will cause a voltage drop that can make the controller reset or shut down.
If That Didn't Work
If you're plugged directly into a house outlet and it still shuts off, check your circuit. Is the outlet on a GFCI circuit (one with test/reset buttons)? These can sometimes trip with the grill's motor load. Try resetting the GFCI. Also, ensure nothing else high-wattage is on the same circuit (like a fridge or microwave) that could be overloading it.
Heads Up
If you're using a portable power station or generator, it must provide a pure sine wave output. Many cheaper generators and power stations produce a modified sine wave that can damage or confuse the grill's sensitive digital controller, causing these random shutdowns. Check your power source's specs.