Why am I unable to Complete a task in a shared list

Why am I unable to Complete a task in a shared list

  1. If you are a list member in a shared list (Not an admin ) then you cannot complete a task unless it is assigned to you.
  2. Only the assigned person will be able to complete the task assigned to him/her. 
  3. If there is no user added in "Assign to" field, then any member of the list can mark the task as complete.

For more information about permissions, you can check "Permissions in WeGoDoo"