ArticlesPSA Error: "Can’t assign permission set to this user, user license doesn't match"

• Unable to assign a permission set containing only PSA permissions to a user with a platform license
• Permission set xxx was not assigned to user see the following error message: "Can’t assign permission set to this user, user license doesn't match"

• Professional Services Automation
• Licenses

Create a new permission set:

1. Navigate to Setup > Manage Users > Permission Sets
2. Click New
3. In the User License drop down field, do not select a User License
4. Enter a Label, API Name, and a Description
5. Click Save
6. Click Object Settings
7. Grant the same permissions as the permission set that does not allow users to be assigned
8. Click Manage Assignments > Add Assignments
9. Select the users to give access to 
10. Click Assign

When the permission set was created, "Salesforce" was selected in the User License drop down field.

Once a user license is assigned to a permission set it cannot be modified