If you configured a DHCPv6 Server and the respective scope of IPv6 addresses. The clients are able to get an IPv6 address from the DHCPv6 server, but still the Clients are unable to ping the DHCPv6 Server in a successful way.
The DHCPv6 server is a Windows Server 2008 R2 based server.

ICMPv6 echo request in the local subnet fails with "PING: transmit failed. general failure"

This is expected. You have published the route on the server, which ends up as a Prefix Information option in the Router
Advertisement (RA) message with the Autonomous (A) flag set, indicating to the receiver that they should configure a stateless address based on the advertised prefix.

Therefore you are getting both stateless (public + temporary) and stateful (DHCPv6-allocated) addresses.

To prevent the stateless behavior, the router advertising the RA must clear the A flag in the Prefix Information option. The result will be a local subnet route and a stateful
(DHCPv6-allocated) address.

The problem with DHCPv6-assigned IPv6 addresses is that the DHCPv6 client does not also create a local subnet route for the prefx in the address. This is the role of the local subnet
routers.

Solution for this:

You need routers that can advertise the local subnet prefix with the A flag cleared, otherwise the DHCPv6 client will generate a stateless address and get a DHCPv6-assigned
address.