I installed High Sierra. The names of children disappeared.

This is an issue introduced by macOS High Sierra.

We resolved the issue in the 11.0.12 update, which is a free maintenance update for all Reunion 11 users. It can be downloaded here.

Another option is upgrading to our current version, Reunion 12. (The issue doesn't affect Reunion 12). More than 80 new features were added in Reunion 12. Information about Reunion 12 and how to purchase an upgrade to Reunion 12 can be found here.