Polycom doesn't work at new network

We configured some Polycom phones (450’s and 335’s) which worked beautifully at our office. Moved to client site and they won’t register. One of the phones was also tried at a tech’s home - still no go. These aren’t configured to use a boot server yet so it isn’t a configuration issue with that. Is there anything in Asterisk that restricts a phone to a certain network once registered? Any other possible causes?