If you have the empty water light lit then that will be why its not heating. This either a blocked or faulty pump at the back at the bottom.
Unplug the appliance.
At the bottom rear is a bulged container.
Lever this open, it hinges out, then lift the top off of it.
Take the hoses off, blow up them to ensure they are clean and clear.
Take the pump out.
Remove any debris in the pump.
Clean out the pump reservoir.
Check the float hasn't stuck.
Take the condenser out at the front.
Clean it out thoroughly.
Reach into the condenser chamber as far as you can and scoop out any fluff.
Reassemble the appliance and try it again. If it does the same again then the pump will need to be replaced to cure this im afraid.
Let me know how it goes.