Whenever you get the message "Your call cannot be completed as dialed"
when you call a number you haven't called for months or years, always
suspect that the problem is a change in area codes.
When it becomes necessary to split up a region in order to create
more usable phone numbers, the phone company customarily programs its
equipment to give a warning of the area code spilt for some months
after the split. But eventually it drops the warning and leaves you
to guess what's wrong.
Therefore when you can't connect, it is a wise precaution to dial the
information operator for the area in question -- (area code) 555-1212
-- and ask whether the area was split in the last few years.
Eventually, it seems, every metropolitan area will suffer code
re-assignment, along with many not-so-metropolitan areas.