Check by sending IPSec packet from one side and check the response from other side. Check the show crypto ipsec sa and see in which end device shows the erroe MM_NO...state will produce the error. Check the ISAKMP profile mataches both the side.
We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...