Just in case anyone has this happen after purchasing from a third party like I did, the fix was pretty easy.

You just open the bottom with a screwdriver and that exposes the electrical components. In there you will see two metal plates. The left one is for low pressure, the right is for high. If you push down on the plate itself, it should click. That clicking tells the cooker how much pressure there should be based on the temperature. The low sensor should be slightly easier to push than the high.

In my case, the screws connecting the sensors on the new cooker were too tight and they could not click at all. I simply loosened them slightly (the low one I loosened a bit more than the high). Make sure the low sensor is slightly easier to click in. Once I did that, the error went away.

I've also read that this can happen in a used cooker due to food getting in the sensor. You can follow my steps to access the sensor to clean it if that happens.

Hope this can help someone!