Server 2008 does not automatically answer incoming fax.

A client has a hp 110 server  with fax server set up as one of its duties. It worked fine for 3 or 4 months then stopped answering rings of incoming faxes in May.
"rings to answer" to 1. The machine does not pick up ring, but if set to manual answer the faxes can be received with no problems. The operating system is Windows Server 2008  Service Pack1