dr is door error
this generation of dryer has alot of control board failures(the relay for the heat burns the terminals for the wires)
you can inspect these relay connection visably by removing the front control panel
you might want to try setting the machine to the fluff/air dry setting and try starting the dryer, if it starts in air fluff you need to check the connections on that relay
this is not a factory taught test.
its just something a customer pointed out one time and i have tried on many after the fact, and for whatever reason these machines will still run in fluff mode when the board is fried
Frigidaire Dryer Control Board Part # 134523200