You may have stumbled on to the reason the former owner sold the items.
As stated in the first reply - check the simple things such as batteries, power supplies, connectors, fuses. That's often the stuff that fails.
Get some operating instructions if you can. Maybe there's a switch (possibly DIP switch inside) to select channel or a screw to tweak the operating frequency. Certainly bands use multiples of these therefore more than one channel is used.
Maybe the transmitter and reciever aren't compatible. I've seen pairs of things from used equipment dealer like that. If there are others around, musicians, etc - they might have similar equipment and be of some help.
If you can determine the frequency of the transmitter see if you can locate a reciever on the same frequency. That's probably easier said than done. Maybe a local radio shop with an appropriate reciever will do a quick check for you - using a reciever to check the transmitter and signal generator to check the reciever.