Carrier infinity with code 47 No 230V to unit - later no power at Thermostat

[Switchex]

I have carrier heat pump unit that was showing fault "Code 47 No 230V to Unit" and the unit was not working. As anyone would do, I flipped the breaker once on/off to see if that would resolve the issue. So when I came back up to check on the thermo, to my surprised, the unit was completely blank, no power, no light, no nothing! as if it was "fried". Later, with the power on, I tested the disconnect boxes and had power going in and out of them (indoor and outdoor disconnect boxes).
With the outdoor unit, I also removed the access panel and tested the contact by pushing it in .. when I push it in, I hear a short start-up buzzing sound that goes away in 1-3 sec. It sounds like it wants to start, but it's not getting sufficient power (capacitor issues?).

So, seems like I have 2 issues that may or may not be related.

1- Thermo is completely gone
2- No power or not enough power at the unit

This is the extent of my testing and knowledge. What is the next step of troubleshooting here? Can I purchase a generic thermostat to see if at least the thermo issue is resolved?
Any help is appreciated.
Thanks.

 

[Fitter30]

Take a pic of the wiring diagram of air handler.

 

[Sponsor]

 

[ArayT]

When you checked for power what was it? Power to your tstat comes from a transformer located normally in the air-handler. Make sure ALL your connections are tight. Loose connections can cause multiple problems.