You may encounter an issue that some of the fields (like checkboxes) in the ticket creation form that are marked as mandatory do not become red during validation when you try submitting the case (while these fields are empty).
The issue that some mandatory fields are not turning red when their are validated once the submit button is pressed may be caused by a custom CSS override on the customer's instance. This custom CSS is altering all the field names, causing the affected fields or checkboxes not to be highlighted in red when they should be.
To resolve this issue, you need to modify their custom CSS - find the line that is causing the issue in the custom CSS in the "New conversation" and replace or delete it.
Please note that assistance with custom CSS modifications is outside the support scope of Kayako, so the users or their web development team should make the appropriate modifications themselves.