How do I resolve issues to add client users to internal tasks?

How do I resolve issues to add client users to internal tasks?

If you face this issue, most likely. Your Task List Flag Setting is set to Internal - Meaning no client user will be added - here is how you can set your task to external. 

(1) First is group your task by 'Task List'

(2) Click on more setting or the three dotted line then choose Edit 

(3) Choose the Task List Flag as External.

(4) Make sure that the client user you are trying to add is added to the project. 


(5) Add them to the Task