The manual says pretty much what you would expect it to:
If the message SELF CALIBRATION FAIL appears, check the following:
• Verify that the test tool and remote are securely connected with the calibration
module.
• Verify that the connected units are resting on a flat surface.
• Check the main unit, remote unit, and the calibration module for damaged
connectors.
If the self calibration continues to fail, send the main and remote units and the
cable adapters to the nearest Fluke Networks service center. See “Service Center
Repair†in Chapter 8 for details.
So, since you have nothing to lose at this point, I would try replacing the software in the main unit and the remote with the latest version. This will erase everything, hopefully clearing the error code in the process. Thing is, I don't know if it will let you, and of course if it continues to fail self-calibration then you really should do what the good folks at Fluke say and send it in for service. But you can find the update here:
Fluke Updates (All the usual disclaimers apply.)
Jim
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I'll give up my 2500 set when they pry it from cold dead ear.