I failed to install the ground wire that goes from the back of the clothes dryer to an external grounding source. My dryer will no longer run. What do I do?

Unless there is something very specific to your model, the failure to have an external ground should not prohibit your dryer from working. I'd first look at the breaker and then at the dryer wiring.

You need to check your wiring carefully because it sounds like you have a wire loose or burned in two which could be dangerous. A missing extra ground would not cause such a problem. DrTom4444