janjust wrotethere is a router or firewall blocking traffic - the initial packets are coming through, it seems, but the replies sent back must get lost somewhere. Check the firewall policies on both sides.
Also, some ISPs and countries filter heavily on OpenVPN traffic - it's hard to duck these firewalls.
I am in china, I just change the vpn port and the problem was solved! Maybe the GFW is great and terrible!