Hello Rick, phone calls are an extra charge, we can likely do just as well in this dialog box.
I need the model number of the Rinnai unit... so far your guess is close, you can try a new remote, or the dealer if he is nearby might let you use one of their spares... if that fails, then it is most likely a problem with the printed circuit board IF you hear nothing what so ever from the unit when you try to get it to fire either from the remote or from the buttons on the front of it.
Let me know about all that, and what you hear from the unit attempting to start.
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.
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.