Hello, I am a customer of the web site just like you are, I am only paid IF and when you have the full and complete answer you need, and then, only IF you choose to rate my work positively... I believe the web site does hold your deposit however until then.
I did not get a comment about a completely blank screen, but thanks for mentioning it now.
You will need a multi meter to check this out. The cause is either a bad thermostat, or more likely no 24 volt power getting to the thermostat from the furnace... you need to make sure the furnace has power, then if it does, we need to measure the voltage between R and C on the thermostat terminal strip inside the furnace blower compartment. There is a 3 or 5 amp fuse on the printed circuit board and sometimes one at the transformer.
Please attach a well focused, close up photo of the wiring diagram glued inside the service panel,you can use the paper clip icon at the right end of the toolbar at the top of this dialog box,Include a picture of the thermostat wire connections to the printed circuit board in the same area.
If there is no paper clip icon, look for the '+attach files' link at left of your send button.
I can mark it up with trouble shooting instructions. You will need a multi meter ($30 at a hardware store) and some experience working with appliances, let me know a lot about your skill sets in those regards.
We can go from there, if I miss you tonight I will pick your response up first thing in the morning.