You'll have to take it to some place that has a plain old telephone line and see if it answers. If not, the unit is defective.
The people at Hp's help desk had me go through a lot of re-starting and downloads, but my HP 2210 MultiFunction just stopped faxing one day. We did install DSL but even after disconnecting all of that it still does not work. It is being used on a system with XP. Everything else about the printer works just fine. The only thing I can think of was an updated driver from HP. Can anyone help? When it dials it sounds different, and when a fax comes in, it says connecting but then does nothing.