Thank You for using JustAnswer - My name is Tony and I am more than happy to help with your question today.I take it you can see the belt going around the drum.Have you tried pulling on the belt to check it's tension.
So when you press start, can you hear the motor turn or does it just make a humming noise.
In your opening question you say that the startup sounds normal.I assumed you could hear something starting.
If the display says clean condenser then this is where the problem lies.Other than that other faults will be notified by error codes on the display.It is possible that the pump for the condenser unit is blocked so you need to think about looking at the tube that is fed from the condenser unit to the pump at the rear.
Did you blow down both tubes. They get blocked with fluff.
Put the condenser unit back and make sure it pushes home fully.Turn off the power at the wall.Close the door on the dryer.Turn power back on at the wall and tell me what it says on the display on the front control panel.
There is a valve that connects the condenser to the back of the housing.There must be a blockage there.Make sure the valve can open in the back of the condenser.