The Unified Employee license doesn't support access to custom objects, unless the objects are part of a security-reviewed managed package from AppExchange. This restriction protects sensitive custom object data from being exposed to broader access than the license is designed for. As a result, you can't assign profiles, permission sets, or permission set groups that include restricted custom objects to Unified Employee licensed users. Also, you can't add restricted custom objects to profiles, permission sets, or permission set groups currently assigned to those users.
Where: This change applies to Lightning Experience and Salesforce Classic in Enterprise, Performance, and Unlimited editions.
How: To give users full access to custom objects, upgrade their user license to one that grants broader access, such as the Salesforce Platform user license.