These are known bugs for Global Data Services (GDS) and Sharding in Oracle Database 12c Release 2 (12.2).
When using an IPv6 IP address for Global Data Services (GDS) or shard database hosts running Oracle RAC, the automatic valid node checking for registration (VNCR) feature of GDS and sharding does not correctly add the IP address to the list of invited nodes. As a result, host registration is refused by the Global Service Manager (GSM) or shard director.
Use the GDSCTL command add
invitednode to add the IPv6 address manually.