vSAN clusters may display "Evaluation Mode" or "Unassigned" license status following an upgrade of vCenter Server from 7.0 to 8.0. This occurs because the major version upgrade invalidates legacy 7.x keys.
vCenter Server 8.0 requires matching vSAN 8.x license keys. During a 7.0 to 8.0 upgrade, vSAN clusters lose association with legacy 7.x keys and default to a 60-day evaluation period.