
4 answers
Cases can be made available to Salesforce Platform License via Permission Sets.
1. Go to the User record and Select Permission Set License Assignments -> enable Company Community for Force.com check box and save.
2. Create new Permission Set with the Company Community for Force.com license
3. Edit your newly created permission set to show Cases. Under Object Settings -> Cases-> Tab Setting -> check "Available" & "Visible". Under Object Settings -> Cases -> Object Permissions -> check CRED and Save
4. Go back to the user and Select Assign Permission Set Assignment -> add newly created permission set