ssh cannot connect -- says "port 22: no route to host"

I have an account at a unix host that I reach vis ssh on my MacBook Air (12.13). It quit working from my Mac a few weeks ago; I can still access the account from another computer (a Windows 8 pc that I use at home for dial-up access -- a remote rural location). When I try the ssh command to login, it says: "port 22: no route to host". Oddly enough, it used to work from a windows 7 pc at my broadband site (my mother's house with Verizon FIOS) but now I cannot connect using putty there. But at home using putty it works fine. I would be grateful for any ideas as to what is going on and what I can do to fix this. Thanks.