Is the non-working scanner able to receive NOAA weather? Do you have the same version of firmware in both scanners? Is the P25 Threshold set the same on both scanners? Swap the locations of the 2 scanners in case we are dealing with a simulcast issue. Which systems are you monitoring? Swap the antennas between the 2 scanners. Check if the center pin on the connector of the antenna is broken off or shoved in. If both scanners are programmed using the same file and the squelch on both is set at 2, the only thing left, other than a scanner defect, is the RF input. What programming software are you using?