So we (the HVAC Department) have run into a roadblock into what could be wrong with a problem we're having with a system we installed. I have absolutely no idea if there is anyone with this knowledge here or if this post at all is even allowed. If it isn't I'll take it down on request from one of the Admins. But at this point, I'm trying every possible avenue of public troubleshooting so...what the hell.

So we installed a rooftop Concord Heat Pump at this distribution center that used to be an old slaughterhouse.
Heat Pump M/N: 4HP14L60P-9A
S/N: 1917C61739
The indoor heat strips I believe do not have a circuit board configuration. It is separate from W1.

Apparently we replaced their old T6 T-stat with a NEST and then it wouldn't go into cooling. When it was set to cooling the reversing valve wouldn't slide over to cooling since the default for Concord is heating. We replaced the NEST with a brand new T6 Pro T-stat and it still didn't do anything. We checked the defrost board and since it was flashing both lights simultaneously (Circuit board failure according to error code) we replaced it with a brand new board and it still wasn't working.

Side Note: This board DOES NOT have a fuse in it.

Only by putting in a jumper wire between O and R on the outdoor condenser do we here the click of the reversing valve and feel it cooling. We have no idea what it could be...well that's not strictly true but we are praying it's not the valve itself. We've already replaced the outdoor unit once. So far we think it's either that or the 24v wiring is bad somewhere. But that doesn't make sense to me because if it were, then either:
A: We wouldn't have anything working
or B: The jumper wouldn't have worked.

Anyone else care to chime in?

Maybe you've already got this fixed?
I don't work HVAC, but do keep half an eye on home automation, and I thought I'd heard stories of how NESTs frequently had a problem like this, at least for residential grade units - where after the install the brand new units wouldn't operate. If I remember the thread right, the issue was that the units were usually not wired correctly for commercial power.

https://www.businessinsider.com/nest-thermostat-problem-2014-1

https://www.hvacproforums.com/threads/problem-with-a-nest-thermostat.19632/

https://www.electronicdesign.com/blog/use-common-wire-nest-thermostat-or-suffer-consequences

I'm curious to hear what's become of this - if you've already got it solved or I'm totally off the mark.

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