Cooling stopped working on my second floor zone, and cold air was blowing out of return air vent.
I turned off the power to HVAC , it didn't work.
When I turned off the thermostat of my second floor zone and turned it on after an hour, to my surprise the issue was gone, cooling started working in my second zone.
I am really curious to know how turning off the thermostat fixed the issue.
Hopefully these images helps to understand the issue