Hi Buddog, welcome to the forum.
You say it heats up, the way it always has. ?
What in 2 hours ??
Mine takes about 1 hour per degree celcius.
So from a fresh fill, it will run for at least 24 hours to get up to full temperature.
During this time, the pump will continue to run.
The heater is buried inside the pipework so requires a water flow.