Unable run a Document Package using the email delivery option on the Task object.
This is expected behaviour, the Document Package will need to be run on a different object. We would suggest using the parent object of the task to run the Document Package.
Unable to Access Page:
The value of the "p3_lkid" parameter contains a character that is not allowed or the value exceeds the maximum allowed length. Remove the character from the parameter value or reduce the value length and resubmit. If the error still persists, report it to our Customer Support team. Provide the URL of the page you were requesting as well as any other related information.
*This error message can also show up if the object you're running the document package from does not have any Activity History.