Sub-task requires Epic Link but system does not all Epic Link for sub-tasks

[Megan.Munro]

I created a new sub-task issue type called "Design Bug". When I try to create and save a new design bug, it fails to save and I receive an error saying "An Epic Link is required to create a Story, Bug or Task" (which implies it is registering the issue type as a Story, Bug, or Task). To resolve this issue, I tried adding Epic Link to the design bug screen & field configuration, but then I receive an error saying "A subtask cannot be assigned to an epic"(see image attached for reference of both error messages)

I have tried to retrace steps and remove Epic Link from the design bug screen & design bug field configuration, but that did not help. The design bug screen is definitely included in my issue type screen scheme. 

Does anyone know why it is processing the issue type incorrectly? 

[Nic Brough -Adaptavist-]

You have set the epic link as a mandatory field for (probably all of) the issue types.

Change the field configurations for the project - you either need to make the field optional, or split them in two, having one field configuration for parent issues (with the field mandatory) and another for the sub-task types (with the field optional)

[Megan.Munro]

I do have two separate field configurations - I actually have one for each issue type in my issue type scheme. 

I have a sub-task called Story Bug that does not require Epic Link. On it's field configuration, it has Epic Link "Locked" (see image), so I cannot change whether epic is Required or Optional. However, Epic Link is not associated with any screen used by Story Bug and when I create a Story-Bug, I am not prompted for the Epic Link. 

I copied the Story Bug field configuration and screen for the new sub-task issue type, Design Bug, so I expect it to work in the same manner. Epic Link is also Locked, but similar to Story Bug, I do not have a design bug screen associated with Epic Link.

[Jack Brickey]

issues of type sub-task should not show under any 'create issue' screen. Sub-tasks are created from the detailed issue view of an existing task/story. Given you are receiving two conflicting errors I have to wonder if you have two issuetypes named "Design Bug", one as a task and one as a sub-task. Referencing your first image, you should not see "Design Bug" in the dropdown of the Create issue screen.

Can you create a Task in the project and then try to create a sub-task w/in the detailed view of that issue? The exact instructions will depend on whether you are on Server or Cloud and if Cloud then are you using new issue view or old issue view.

[Megan.Munro]

The image I posted above came from me trying to create a subtask within the detailed view on an issue. I selected the "+" under subtasks, selected the subtask type (since I have 3 options), and when I pressed enter, I was prompted to fill required fields (of which the only one is Epic Link)

[Jack Brickey]

so you are on Server version it appears. I think that Nic's response is in fact the cause so suggest you follow his recommendations.