When can inactive assignment rules be run on leads?

During lead import.

Inactive assignment rules cannot be run on leads.

Assignment rules are used to automatically assign leads, cases, and other objects to users or queues based on certain criteria. When an assignment rule is marked as inactive, it cannot be used to assign any new records.

When a new lead is created, the assignment rules are checked to determine which user or queue the lead should be assigned to. If an assignment rule is inactive, it will not be considered when the lead is created. Therefore, inactive assignment rules cannot be run on leads.

To use an inactive assignment rule again, you must reactivate it. Once reactivated, the rule will be available to assign new records according to its criteria.