Water Temp Gauge Stuck
 

My son hasa 2000 Ford ZX2 with a 2.0L engine. I just had the waterpump replaced a month ago because it was squealing. I was driving it today and noticed that the water temperaturegauge needleis stuck in the middle of the gauge and it doesn't move (it stays in this location when the engine is running or off). Can someone provideme with advice?