By default, if finalization has not begun in 3 days of time since the Packaging Machine was created, the task will be canceled with a timeout error.

On the ELM logs, you may see something like the below:
2020-01-02 13:43:59,486 ERROR [61605]        CompositingEngineP: Timeout occured after 2.23:58:59.8051620 waiting for packaging machine to initialize finalization for work item 25165945.

This is by design. 

To change this, go to System -> Security and Retention Settings -> then select Edit in the upper right corner. The "Packaging machine maximum time to live (days)" setting defaults to 3 days but can be extended to 24 days maximum. Once this setting has been changed it will be applied to all new layering tasks. Any existing tasks will still use the prior value.