Could be four things:
1. Your system firewall is blocking the game
2. Your router firewall (if you have one) is blocking the game
3. Your ISP (Internet Service provider) is blocking the game
4. SRO for some reason banned your IP (most likely not it).
Solution to all but #4:
Check to make sure that you have these ports open:
15779 (Login)
15881 (Patch)
15883 (Play)
Thanks RMP for the awesome research:
Linkage