Insure that there is no splitter in the cable line between the preamplifier and the preamplifier power supply/power inserter.
Insure you have properly installed the preamplifier per the instructions.
You cannot have any standard splitters or an amplifier, in the line between the Preamp Output and the power inserter "TO AMP" port. They would block he voltage from getting to the preamp.
Try replacing the cable between the preamplifier and the power supply.
Verify that a preamplifier is needed by visiting www. antennaweb. org.
CM-7777 CM-7778 CM-7777HD