Thermostat won't work.

[Maryam3]

It says the RH isn't connected but it is. I can't even use the thermostat because of it.

[CoolingWizard]

@Maryam3,

You need to ensure the RH bare copper wire is straight, and proper length.  Ensure it is fully inserted.  If you forgot to turn off the power before you removed your old thermostat and installed the new Nest thermostat, you might of caused short circuit that blew the 3-amp fuse on the HVAC control board.  

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The AC Cooling Wizard