The reason why your Scheduled Task is not triggered is because it is configured for the Domain-DNS object type, but your Business Unit includes Users only.

Based on the LDAP filter that you use for your Business Unit, it doesn't include any domains, and thus there is not a single Domain-DNS object in the Business Unit that the Scheduled task can be triggered on.
The best way to resolve the issue would be not to use a Business Unit, but rather have the LDAP filter hard-coded directly in the script. If you are OK with such a solution, we'll help you to modify your script.