Be more specific about what you don't understand and we'll try to clarify.
There are a couple of things to understand about
narrowbanding - not only is the deviation (you can think of this as the amount of space the freq takes - and before I get flamed, yes that is a vast oversimplification) reduced, but if the power or the height of the antenna is reduced, it's going to be harder to hear. Think of a flashlight with a Krypton bulb - these burn quite brightly and can be seen for a great distance. Take that flashlight and put it near the ground, and the distance you can 'see' the light is vastly reduced. The concept is not all that different for radio.
If you are using this frequency with a tone (either a PL - otherwise known as Private Line - and perhaps more complex as
CTCSS - or
Digital Coded Squelch, which is somewhat different), it's possible that the deviation for the tone has been reduced too far for your scanner to pick it up reliably. That is why it was suggested that you try listening without a tone. Or as I had suggested, just sit on the frequency with no squelch and see what develops.
Incidentally I've put some links in here - they're in blue - from our online wiki glossary to help explain the terminology.
In any case it would seem, at least at first blush, that reprogramming the frequency as a narrow band FM mode would solve the issue. I'm not up on the RS object oriented scanners, but it shouldn't be all that hard. You didn't say if you were programming this with software or doing this by hand...that is assuming that the issue isn't being caused by a power reduction (just as likely) or an antenna change at the transmit site.
best regards...Mike