Configured WCC's EEM policies to grant user who are in a specific global group access to WCC but they are all getting denied access.
Review EEM UI -> Configure -> User Store -> Group Configuration -> Global Group Configuration -> Group Resolution Level
Set it to "Resolve direct groups"
Click Save
Confirm the user's global groups are seen by displaying the user's details under Manage Identities or run a Permission Check against the user with the "Display debug information" checkbox enabled.