First, the Kenwoods & Icom NXDN's are monoband, that is either VHF, UHF, 800, etc., but not multiband.
So you'll need the correct band radio.
Second, Some older Icoms are only 6.25 kHz (Very Narrow) bandwidth and won't copy NXDN traffic on 12.5 kHz (Narrow) systems.
Third, if encryption is being used, you won't copy anything unless you have the encryption key.
Last, if system is trunked, you won't copy anything unless you have the system key.