Honeywell t8000c display is blank, unit doesnt run

I would say that you have one of two issues. Either your thermostat is bad or you do not have 24v coming from the heating unit. In this case the problem would be in the low voltage circuit of the heater. At the heater you should have 24v AC when you place an electric meter across the R terminal and the C or W terminal. If you have no vaoltage across the R to either the C or W then you have a bad transformer or a blown fuse in the furnace. If you do have voltage ther and also at the t-stat then the t-stat has gone bad, replace it.

First, remove face plate and on wall plate you will see about 6 or more straight sensors or prongs sticking straight out towards you, on the bottom. They go into holes on face plate. Make sure they are not bent. If they are bent then, they will not go into the holes in face plate and nothing will appear on your screen nor will furnace run. They are easy to straighten with needle nose pliers, but be gentle so not to break them and when you put face plate back on, do it gently to not bend anymore.