Can you double check that that SPX 50.......... model number again, its not coming up in the
manufacturers service manual files.
Lacking that, there should be a wiring diagram
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.
If none of this in your skill sets, tell me which direction you are from the center of the nearest city and I will look for a few well rated service outfits in your area.
We can go from there.