inlet cryo unit issue

Hello, I have a 7890A that has an inlet cryo unit installed. About 5 years ago, the cryo unit was turned off.  When I went to turn it back on, under the config screen of the instrument, it says that cryo is Not Installed.  I've opened up the instrument, and followed all of the wires and they all seem to be plugged in.  Any idea on why it is saying that it is Not Installed?  I have no previous data on why it was initially disabled 5 years ago, only that it was working before it was turned off.  Thank you!

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