When the Task Active State Management Business rule changes a tasks from a closed state to an open state, the Active flag is only set to true when the new state is the default open state. Otherwise, even if the state is not in a close state any longer, its active flag is still false.
Steps to Reproduce
1) Open a Task record.
2) Change the State to "Closed Complete", "Closed Incomplete" or "Closed Skipped". The Active flag gets set to false.
3) Change State to "Work in Progress" or "Pending". The Active flag does not get set back to true.
1 - Delete/deactivate the Business Rule 'task closer' (sys_id=475ef3c5c611228401440a7a5f29a786).
2 - Delete/deactivate the Business Rule 'task reopener' (sys_id=424c5600c0a8020e00d3202817312821).
3 - Import the Business Rule Task Active State Management.
4 - Import the Script Include TaskStateUtil.
5 - Create Dictionary Overrides for the State field on the Task dictionary for extensions of Task if the default values in TaskStateUtil are not correct for a table.
NOTE: Step 5 is very important as it can cause issues when the State of a Task is changing by changing the Active flag unexpectedly.
Related Problem: PRB1370868