What signal are they taking about?
The meters send their data back via a wireless mesh network. They can talk direct to DCC (the government company that collates the billing data), or talk with each other to transfer data around.
If you're in a bad signal area, you can't talk to DCC, and there aren't enough other smart meters around to make the mesh network viable. It's also possible that your meter is somewhere (such as a basement) where it can't get a signal out.