Disconnect vent Check for hot air coming out,If yes run a cycle if it dried normally.your problem is not the dryer.If no heat ? It gets complicated fast.Make sure you have nothing blocking air passage inside of vents inside.This can be where your sock went.Or a rodent made home in there.I have pulled snakes racoon babies rats you name it birds,Yes some were alive.If not that then the issue will reside with the heating source,That involves thermostats safety fuses heater coils wiring and a whole lot of hands on checking.There is a switch on the motor which limits the flow of power to the coils if proper spin speed is not achieved.Safety first Call a tech you mess with things beyond your scope you can massively fail. Pay for confidence .