Authorisation levels are set to prevent standard users from being able to delete high security tasks.
Security levels per task category are set within Task Categories within Proclaim.
The security level of the task needs to match or be lower than what the users security level is set to within User Profiles for the user to be able to cancel the task.
Task Categories - Security Level required to cancel tasks
User Profiles - Main Tab - Security Level
If you do not have access to check the security level, please raise a new case online and reference the title of this article.