I just went through this problem with my car, which is the same as yours: an 07 base with 64k miles.
I noticed that one of the four tire readings would go blank first (left rear), so there would be three numbers displayed. In the position for the left rear, only a "--" would appear. Within minutes, I would see the "inactive" message, and all 4 readings would show the "--"
I replaced just the one sensor, and all is working properly again. I bought an extra sensor for when the next one goes.
Relatively older and higher mileage cars like ours are starting to show this now. I suspect the problem on your car is not the receiver, but the sensors, because the sensors are near the end of their useful life. And it sounds like at least two of your sensors are bad.
The theory goes that using the car wears down the batteries in the sensors more quickly, so cars with fewer miles aren't having as many TPMS issues yet.
When you buy the sensors, check the dates printed and stamped on them. They have a limited shelf life.