When replacing an ART-2000 or ART-2100 radar receiver transmitter with a loaner or replacement unit, make sure to check that the antenna switch settings are set to the proper flat plate.
The normal engine startup sequence removes power from the avionics system, causing it to drop offline. SB560XL-24-14R2 prevents this occurrence.
The problem could be with the remote vertical gyro valid missing due to the gyro not being valid, or it could be the ADI itself is not positioning to where the gyro is telling it to be.