My dryer clicks when it starts and nothing happens, no error codes appear, why?

Most likely it is dirty and lint deposits have built up, as it always does, in all the air ducts which will cause the main safety to blow causing the problem you described. The thermal fuse is behind the drum and positioned so that you will have to take the dryer apart to get to it. There is more than one fuse most of the time. You need a multi-meter to find which safety has blown. You will have to take it all apart and clean the drier out thoroughly or it is all for nothing. Every air duct will have to be removed and scraped and washed out to remove baked on lint deposits which bakes on like a concrete lining. This will burn so the manufacturer has installed the safeties to keep from having a house fire. The safeties are oval-shaped with a round center part containing the safety with two plug-on terminals for the wires and when they burn open, from the dryer being dirty, nothing will work or it will not heat. Using an ohm meter you put a lead on each terminal of the safety, with one wire unplugged, and if it is good you will have a reading of about zero; if it is bad it will read infinity. On your dryer you may also have to test some thermistors if it has them. They are sensors that are around in different places to test the temperature and you test them with a meter set to ohms and compare the reading to a chart. They are specific to the dryer, but if you read nothing or a short you will know it is bad. Probably, once you clean it the dryer will run find after the blown safety is replaced, too. Driers were the number one cause of fires at one time, hence now we have safety fuses. Look at: How to clean your clothes dryer. How to make it hot again. - YouTube (http://www.youtube.com/watch?v=MMP7BW1lLs4) to see how. Also look at these to get an idea about how to clean it: Mr. Appliance Tips: How to Clean Your Dryer - YouTube (http://www.youtube.com/watch?v=iBiRw-KElC4) ; Cleaning a Dryer Vent and Lint Trap - YouTube (http://www.youtube.com/watch?v=yFTZGgVisCI)
Electric Clothes Dryers (http://www.electrical-forensics.com/Dryer/ElectricClothesDryers.html) Dryer vent cleaning prevents fires - YouTube (http://www.youtube.com/watch?v=A6wmD502-xE) and: Cleaning out a dryer with top lint cleanout - YouTube (http://www.youtube.com/watch?v=OBNDbyRm68M&feature=fvsr)
Cleaning out a dryer: By a woman 2 of 2 - YouTube (http://www.youtube.com/watch?v=a73HTFkcB90&feature=relmfu)
If you tell us the model I can supply a manual. You will need a good meter to find the blown safety. You test it like a fuse.