Classes in new git branch not available to foreman?

I branched my git repo, added some classes. Want to assign one of the new
classes to a node but the class doesn't show. How does repo decide what
classes to show in the GUI?

Good day.

First of all I would suggest to check foreman access log. Most probably you
have syntax error in your classes.
Foreman uses following command to check syntax during import:

puppet parser validate openssl-wrapper/manifests/init.pp