1. If using a profile, such as the Partner Community profile, set the cases tab setting to Default On and enable the “Read,” “Create,” and “Edit” object permissions for cases.
2. If using a permission set, create a permission set with the following settings for cases:In the Tab Settings, select Available and Visible.In the Object Settings, select “Read,” “Create,” and“Edit”.
3. In the Tab Settings, select Available and Visible.
4. In the Object Settings, select “Read,” “Create,” and“Edit”.