Answer
The scopes field in argocd-rbac-cm tells ArgoCD which token claims to read for subject matching (commonly groups, sometimes email). If it doesn't reference the claim your IdP sends, g bindings won't match and users fall to the default role. Correct scopes are essential for SSO group RBAC to work.
data:
scopes: '[groups, email]'Real-world example Adding groups to scopes fixes users landing on readonly because their group claim wasn't being read.