You are unable to see the external members as members of a group provisioned.
MNE can provision external members of a Domino group. The process involves the typical group provisioning process.
1- Verify that the NME Database is up-to-date and you could view the members of the group with the external members in it.
2- During the group provisioning process, verify "Add contacts for member not found ind AD" is selected
3- Go to AD and find the OU you specified in "Path to existing OU for creating external member"
4- Find the external contacts and properties
5- Find "Attribute Editor" tab and put a filter that shows you only attributes that has values and writeable.
6- Verify TargetAddress or ProxyAddress match with what you have in Domino
