There is a known issue where IPv6 tunnel routes may not be added to the routing table on iOS 7.0.x. This issue was fixed in iOS 7.1 Workaround: use redirect-gateway instead of pushing specific IPv6 routes. For example, in the server configuration file:
push "redirect-gateway ipv6"
Or the client configuration file:
Note that iOS 7 and higher requires that if redirect-gateway is used, that it is used for both IPv4 and IPv6 as the above directive accomplishes.