The NAC you reference, 345, is the one used by the Tuscarawas County site for the statewide MARC-IP trunked system.
View attachment 87969
None of the Whistler scanners support entering the site NAC for a trunked system. Only the Uniden SDS100 & SDS200 can use that detail, but that's really to prevent transmissions, on the same frequency, from a different site or system. If you are entering the site frequencies as conventional, with the NAC of 345, you are only hearing scattered pieces of conversations being carried on the site.
You did not specify which scanner model you are using, only that it is a Whistler radio. Presuming it is a digital capable scanner, you need to program this site as part of a trunked system, then you can enter only the talkgroups you want to monitor, whether that's only fire & rescue, or something else.
Note that there are two other sites on MARCS-IP, located in your county as well as the Tuscarawas County site.