When using a Property Validation Rule with a Type of Checkbox and setting it as Required does not make the Property required, ticket can be saved without checking the box.
Applies to all supported versions of Service Desk Manager.
This behavior is correct. A checkbox really has two values, checked and not, there is not a NULL value, the default is not checked so that acts like a value.
There is a simple solution, create a Validation Rule that is a dropdown, set required, add two Property Values, such as Yes and No. This will require the user to select one of the values before saving.