When you configure the "Assignment Task" action in your workflow designer, there are 2 required fields you need to set. (1) the assignee of the task (who this task will be assigned to), and (2) the task form realted to this task (this is the page that the task owner will see when check the task information).
If you are not set the associated task form for the Assignment Task, you will receive the error message like below:
This means the Assignment Task with name "Assignment Task_1" does not have the selected Task Form.
To resolve this issue, please go back to the workflow designer, select the Assignment Task, and select the task from from the dropdown list.
If there are no available Task Form from the dropdown list, you can create a new Task Form from the form designer.
(1) Go to the Forms Designer
(2) Click the form title on the top-left, and from the dropdown list, click +Add task form.